Why do you need a stake to kill a vampire?

Personally, I don't think staking a vampire will do anything other than seriously annoy them and injure them very badly and weaken them, which will only make them want more blood, meaning more murders, especially yours if you're the one that stabbed them in the first place. But I don't see how it would kill them, seeing as their hearts don't actually beat.

Slitting their throat might do the job, though. Or suffocating/drowning them, I suppose.

Very hard to kill a vampire.