Meter is defined as the distance travelled by light in vaccum in 1/299792458th of a second.

No, it isn't. The speed of light is 299792458 meters per second. The meter was not defined as someone saying "Hey, let's get a drunk guy to spew a big number and divide the speed of light by it". Depending on the story you believe, the meter was initially either based on math related to gravity or as a function of a quarter of the Earth's circumference.

Because, once you realize that (modern) imperial feet are a function of standard meters anyway, you can make the same claim regarding it being a function of the speed of light. I just don't care enough to do the math on that one.

Would use 180 cm which is not as hard to remember, with more precision. Also why 6 feet specifically? 160cm becomes 5 and a quarter feet which is pretty messed. My argument here is bad because we are comparing magnitudes of units, which is useful in different scenarios. But i see no problem that is not fixed by dividing or multiplying the current one by powers of ten and calling it centi, kilo, mega, micro, etc.

In the western world, 6 feet is a pretty common reference since adult males tend to cluster around that height range. So if you are guesstimating the height of someone or something, you can use a person you know is "about six feet tall" as a reference. Same thing with ceiling and door heights. Which speaks to cases where precision is not important and is actually detrimental.

Because, in every day life, we don't need or want that level of precision. If I actually want to know how long something is to the centimeter (or beyond)? I'll get a tape measure. If I want to estimate where the middle of my climbing rope is after the middle mark has worn off? I can use arm spans to get "close enough" that I can rappel in any situation where I am not going beyond 20 something meters (and you can bet that I am guesstimating a meter to be approximately a yard in that case...). If it really matters? I am getting a reference (in that case just pulling up both strands).

Not just the scientific computing, but imperial system is harder to learn because there is no specific fashion in the units. How much inch is a foot and how much foot is a yard(?). Actually i don’t know thoose they change between 6 and 12 and maybe more different numbers.

No arguments there. I still have no fucking idea how long a mile is and will never know (... beyond it being approximately a mile at highway speeds, adding in a buffer for traffic). That said, "foot" is actually a pretty good name because that can generally be approximated with an adult male (yay sexism)... foot. I know my foot is about ten inches long (I am dainty) and can do quick estimates at room scales based on that. Same with knowing my stride is about 3-4 feet which is about a yard.

But also? It doesn't actually matter. Because, again, people don't need that level of precision in their every day life. Again, if I want to know the dimensions of a room, I get a tape measure. If I want to know if a chair will fit in the corner? I can guesstimate by arm spans and so forth. If I get close? That is when I get the tape measure out. Otherwise? It genuinely does not matter

The thing you are talking about is water’s volume, which can make water’s density a standard and measure densities of other fluids relative to water. But the conversion factor of 10 is the most advantageous thing which is also simple.

Scaling by powers of tens and arbitrary constants are more or less the same as far as a computer is concerned. And once you consider that so much of scientific computing is a function of constants anyway, you aren't actually getting that much if you are using metric versus imperial so long as you understand what units you are converting to what units.

Because...

The solver assuming any unit is hilarious. Units must be always specified. You can’t take a measurement in terms of some units and then not say the units. There is no point of using exact same units(without scaling) just to be consistent. You are supposed to use different units for different scales.

Exactly (although there actually ARE a lot of unitless solvers in certain fields because you put things in terms of the known constants). At which point it genuinely does not matter so long as the interfaces are documented and the scale makes sense for the math being done (which is more about floating point precision).

We all rightfully clown on NASA for lawn darting Mars because they were using imperial gravity instead of metric. But the reality is that it shouldn't have mattered and the problem was not one of some asshole wanting to use ft/s and instead a miscommunication and lack of standardization/style guide amongst the team.

Personally? I prefer to only use metric when speaking anything scientifically. But I also am under no illusions that it makes a meaningful difference in the age of scientific computing.

But the big issue whenever this crops up is that people insist that precision is what is important. And... for science, yeah. But you are using tools for that if it truly matters which gets us back to the same lack of a meaningful difference.

But day to day? That is all about estimates based on references. And there is a LOT of benefit to coarser grain units that are largely designed around human measurements. Because, I don't know about you but my brain and eyes are not good enough to guesstimate to within a centimeter. But I am pretty good at getting within 10-15... which lines up well with an imperial foot.

And I made a big deal about how 6 feet is a good baseline but... even then it is less "oh, Jan is 6 foot 9 and they are slightly shorter so they are probably 6 foot 5? 6 foot 6?" and more "They are a bit shorter than Jan" which is enough precision to convey someone's height to a friend so long as we both know Jan.

And I do a lot of rock climbing. And that is where stuff gets REAL stupid. Because we all more or less know that 200 pounds is one kilonewton (actually 224.8-ish). So we tend to guesstimate forces involved to know whether we need to find an Edelrid Ohm for a belayer or what by roughly approximating body weight to 200 pounds. Which is not that dissimilar from approximating one kN as 100 kg (at Earth's gravity) but, at that point, we are already using percentages of a reference.

And that is the actual important thing. If you are trying to communicate data with precision? There is no reason to NOT use metric but.. that is more just because most of the world uses metric.

If you are trying to use measurements that make sense in real life? Use references that make sense for what you are measuring and the precision you can expect.