Why Do We Use Slytherins In Harry Potter

Slytherins are obviously much better than those overrated, reckless Gryffindorks. We're cunning, ambitious, and resourceful. We have our own role models, even though some were affiliated with Voldemort, that doesn't change that they did some good in the wizarding world. Most importantly, the guy that brought back Voldemort and the guy that let Voldemort inhabit his body weren't in Slytherin. “Perhaps in Slytherin you'll make your real friends, those cunning folk use any means to achieve their ends” (Sorting Hat, Philosopher’s Stone).

To those who have no idea what I'm talking about, in the Harry Potter series, there are four houses in Hogwarts. When young witches and wizards attend the school in their first year, they're sorted into one of the houses based on who they are as a person. Those houses are Slytherin, Hufflepuff, Ravenclaw, and Gryffindor(k). Slytherin, my house, values ambition, resourcefulness, being cunning, self preservation, fraternity, and traditionalism. Hufflepuffs are hard working, kind, loyal, play fair. People
Not everyone involved with Voldemort was a Slytherin. Like Peter Pettigrew for example, betrayed his friends, got them all killed, and brought back Voldemort. What house was he in? The beloved Gryffindor house, where everyone is a do-gooder. Professor Quirrell too, supported Voldemort, by letting him inhabit the back of his head, and he was a Ravenclaw. Don't forget about Barty Crouch Junior, the son of the head of the magical law enforcement in the Ministry of Magic. We never knew what his house was, but people speculate that he's a Ravenclaw because you have to be incredibly smart to be able to masquerade around Hogwarts as Mad Eye Moody using a polyjuice potion, and messing with the Tri-Wizard Tournament. Even though it's an extremely cunning thing to do, it was never confirmed what house he was