It really isn't just that most of us are lazy (believe me we are) its that we don't have real alternatives.
Are you locked up in some institution? There is a libertarian party, even as a non-US person I know that. And in many countries there is a pirate party. If people don't vote those, they get what they deserve.
Of course the large parties are all the same, their "politicians" are actors and they are performing quite well.
In the US, third parties don't really push this as much as they should, but the US is not just a de facto Two Party system, it is encouraged through most states' laws ("to prevent confusion among voters"). It's extremely expensive and otherwise resource-intensive for third-party candidates to get on the ballot in most states. If the party doesn't pick up somewhere between 1-5% of votes in a state in the previous election (and it resets each cycle), they're not allowed to get on the ballot without tens or hundreds of thousands of signatures. Third party campaigns are mostly a battle to get on the ballot, and much (sometimes all) of the funds donated are going toward that instead of any type of marketing. While Two Party candidates are out campaigning, Third Party candidates hitchhiking to different states to collect signatures.
While there is a Libertarian Party, Constitution Party, Green Party, Socialist Party, and a handful of others -- they can receive millions a year in donations, but still not even appear on the ballot in a given state. The Libertarian Party in particular seems to like measuring their success by how many ballots they get on instead of how many votes they pick up, because that's the metric all the time and money's being spent on, while other third parties are lucky to get on the ballots of a small handful of states with relatively lax ballot laws.
Ballot laws are generally less intense for Congress, but the donor/volunteer pool is also much smaller for congressional seats, and third parties are largely seen as a joke in the US, so even if they got on the ballot, the same "oh, I can't vote for him because he'll never win" mentality will persist. People in the US rarely vote for who they think is the best candidate, but assume there are two viable candidates and that they must pick between those two to not waste their vote ("lesser of two evils" mentality).