1. thq didn't have enough money, so if thq still owned it coh2 will still be in the dark.
2. sega doesn't care about coh2.
1. THQ spent money on promotions. Sometimes they spent it stupidly, but they spent money on marketing.
2. SEGA cares. The thing is going to things like E3, PAX, GamesCom and all that costs money. Floor space, flying the dev team out, swag and so on. CoH 2 has been out since June and we don't yet have anything new to see. We've been at 2 E3s, Pax East (in some way), last year's GamesCom probably a few other shows as well as things like the E3 Judges show.
So are SEGA going to spend a lot of money to let people see CoH 2 when it's both already out and was there last year? No. Because people go to shows to see new games and to be the first to get their hands on things.
It's also a lot about getting your game in front of the press. The press has all played CoH 2. They're not going to write a story about it, unless something new happens. Bloggers and industry fan sites aren't going to write anything about the game, because again it's been out since June.
If we were launching in September and we weren't at GamesCom then that would be kind of curious. But we've been to GamesCom, we don't have anything new to show yet and SEGA has games coming out pretty quick that would be better to show off (Rome 2, Football Manager).