For the same reason there's a .sucks TLD. There's a market for it.
On the other hand linux.rocks and windows.rocks are taken (no website), vi.rocks is 200 USD/year and emacs.rocks is just 14 USD/year.
microsoft.sucks redirects to microsoft.com, but microsoft.rocks is just taken :thinking:
On that note, I've been trying to see if GoDaddy will buy a domain and resell for higher price by searching for some plausibly nice domain names on their site. They haven't took the "bait" yet.