On one hand there's the "Why fix what's not broken" mindset, then there is also the idea the the Browns offense as a whole is a lot better. So while they've been good with Holcomb, they might be awesome with Couch. There's no one, going into the season, that would have told you Holcomb was in the same league as Couch. I agree they need to give Couch the start, else why, coming out of training camp, would they give him the nod over Holcomb.
The coaches know who's the better QB. But play on the field is what means the most. Give Couch the nod, if he stinks it up, you know you've got a solid backup to stick right back in.