There is a reason. It's because PC manufacturers don't have to look at and test every line of code like console companies do. Sony and Microsoft have a more direct relationship with the machines they make and would be held accountable if a patch or piece of DLC messed up someone's console -- they might even have to replace the console at their own expense.
Well from what I've heard, they originally 'programmed' it for the xbox360, then instead of programming it for PS3 also they 'ported' it to the PS3, so its like a makeshift version on PS3 I guess which is the root of all the troubles. Also wouldn't get my hopes up but from what I been readin on the intranet, the newest DLC supposedly is coming out for PS3 in early 2013, with a half-arse tidbit that the other two will come after. Wouldn't count on it though but if they do, awesomeI've loved BETHESDA ever since I played Fallout3. If they were so awesome then & all dlcs up till now work on all platforms, then why not now? What's the big screwup!? I'm tired of hearing dawnguard does this & dawnguard does that & the same for the other dlc. My understanding is its on the crappy 360,but can't be on the ps3??!! What the hell!?