But because we have the system we do, entirely based on simple majorities of votes, sometimes tactical voting matters. For example, if you live in an area where the tories usually get in but the lib dems come second, voting lib dem means one less tory mp. Whoever gets the most votes, even if it's by 1, becomes the mp. And in parliament, if a bill gets most votes, even if only by 1, the bill passes (I'm simplifying a bit here)