Because it's easier to port a PC game to the 360 than the PS3. This looks like a low budget game, and the developers might not have the necessary funds to port it to a console that doesn't has as much players.
Whenever a game doesn't get released to PS3 it always seems to be that the dev's didn't have time or didn't feel like converting it to PS3 format lol. I wonder if it's the same for games that make it to PS3 but not to 360... --- You came alone? Are you TRYING to die? -Cao Xing (Dynasty Warriors 5)
It's not about feeling like it, for a budget title it's easier to go to 360 from PC whereas a third platform which is also more difficult to program for would certainly cost more resources that they probably don't have.