Who do people upload videos of them singing when they can not sing?

Ive seen soo many people on Youtube who can not sing at all, on other words they sound like a horse being mutilated. Such as that girl who sung Tik Tok and Nicole337 among others. Yet they have so many clips of them singing. And they get all this hate mail and they still carry on? Why? Does anyone else find this strange and annoying? XD