Adding to the other answers... This is kind of just "for show" in that most of the time you only use the relevant terms, I can't even imagine what type of problem you'd have to be solving to need to write all this out. Really it's just "here are all of the interactions" and not "oh shit we have to do some particle physics stuff get out the monster equation."

They add ... sometimes to signify that they're just taking pieces.

[–] Instigate@aussie.zone 1 points 5 months ago

I assume one of the only scenarios in which you’d need to use this full Lagrangian is when developing a virtual universe whose laws mirror the Standard Model of Particle Physics. We’re nowhere near even close to being able to do that in any genuine capacity, at least not until our quantum computing gets up off the ground and properly developed.