For things like ballot initiatives you have a point but for choosing candidates there's really not much to be informed about. You usually get the choice between two well credentialed politicians whose beliefs are and policy directions are almost entirely aligned with their party. And the gap between the parties is wide enough that just about everyone will strongly align with (or be repulsed by) one of them.

So beyond the party heuristic it's not really surprising why people don't bother wasting the mental energy.