Because you're complaining about people who you believe don't vote the way you want them to (in this case, not casting a vote). I mean, if you want to do the same thing you're criticizing people for, then you must at least believe that you are subject to that criticism. You think they're harraunging you for voting for someone while not visibility engaging in putting in the work. How is complaining about those people any different?
Let me be clear: the Democratic party and particularly the Biden campaign is failing hard at giving people something they want to vote for. They have gone all in on being a protest vote against Trump, and that's not very exciting, especially given the strong misgivings people have about the Biden Administration's role in supplying the weapons used in Gaza. Like, what is the Democratic Party planning to do to reach someone in Southeast Michigan who lost relatives to weapons Biden's admin sent to Israel? Who voted "uncommitted" in the primary because of that? Because I haven't seen anything besides "Trump would kill more of your family" which rings awfully hollow. This is in a state that was fairly key to Biden's previous victory. So, what work is being done on the ground to reach out? Like, that's the sort of things that actually need, like, visibility campaigns, so if that work is being done, why aren't showing off the work they're putting in?
The way I see it, so much online arguing is devoted to people complaining that "do-nothings are complaining about how I plan to use my vote!". There is so much more that can be done outside of elections and GOTV that spending all our efforts solely on the elections is a grave misuse. You think the people complaining about people voting for Biden and Trump are sitting on the couch and not doing anything? Encourage them to get out and do the things that make it so we don't have to vote for the same horrible dichotomy every four years. Are they doing the work? Encourage them to give visibility to the work they're doing (or the work people like them are doing). Stop complaining about how people handle dealing with bad choices in a system that isn't really responsive to them.
If you vote with the hope that it will fixes problem by itself, you won't get very far. Voting is sort of the end of a political process, the other end starting in people building political movements. For your vote to mean something, you have to be voting with a political project. So, focus on the political projects: start building the structures that protect people first, without relying on the government's approval. Support your communities of care and build your mutual aid networks. Don't wait for it to be delivered from on high, get with people who also care about the things you care about and start using what you have to build what you can.