A grassroots campaign sounds like a significant expenditure of effort compared to voting and casual conversation about the issues. Perhaps maximizing our influence on the votes of others is not the only consideration, and voting hits a sweet spot which returns acceptable values for "(potentially) having an effect", "not too time consuming", and "improves my self-image".

You're right about setting aside some time for research, though; it'd be nice if we maximized potential effect in the correct direction :P