I met comic artist Michael Avon Oeming at Long Beach Comic Expo 2016. He worked on comics for Team Fortress 2, Left 4 Dead 2, and Portal 2; all stellar works if you haven't read those yet. We chatted a bit about his time at Valve, including telling me about Gabe's knife collection, one of which was carved from the bone of a whale's penis. No, I didn't make that up.
Of all the knives, I especially don't want to be penetrated by that one
Just don't ask him when Half-Life 3 will be out, and you'll be okay.
So that's the reason why there is so many knife in CSGO