because it's now on the PC, where most gamers play

no, really I think it's because of a few reasons
-before Bad Company 1, the 360 Battlefield game was Modern Combat 2, which wasn't that great.
-Bad Company 1 had a lot of weird interface and control issues compared to Call of Duty 4 at release. To run, you had to hold down the left thumb stick, there wasn't great feedback if you shot an enemy, the healing system was a bit odd (especially in single player). I heard a lot of the oddities got patched, but the demo doesn't reflect those and it's hard to get people back once the damage is done.
-Battlefield 1943 was cheap on XBLA/PSN ($15 I think) and successful. Had a bunch of fixes that Bad Company 1 lacked.
-Bad Company 2 demo is awesome. Even before the demo, all the videos they released looked awesome.
Even though I'm getting it on PC, if I wasn't, I would have bought it on 360 for sure.