In that way, if no other, voting does serve to support the existing system.
The amount and percentage of non-voter signals to most politicians that people tacitly approve of the entire system. After all, if they disapproved of something about it, they would’ve at least bothered to show up and vote, right?
There’s no better “the status quo is fine” indicator than not even giving enough of a shit to show up at the polls (or in some cases return a slip of paper through the mail).
In a world where refusal to participate is indistinguishable from being too lazy, complacent, or satisfied to participate, and that is the one we live in.
Do you think politicians are going to go check why you didn’t vote? It’s basically as if you don’t exist to them.