Bethesda's TES games are single player because multiplayer games need small, or very low-detail maps. Not only that, but the tech infrastructure that goes into the engine just to support the connectivity is huge, which reduces the developer hours that you can put into the game itself.
it's a huge undertaking to make a game mplayer, and in a TES game that is already huge, it would spell major cutbacks for the series. And seeing how people complain about the state of the (rather well done) game right now... I'd hate to see what would happen if we lost any functionality in place of multiplayer.
Yeah, your point is valid, but I hope you're realising what kind of "multi-player" we're talking about here.
Not deathmatch, or player vs player gameplay. I'm referring to open world co-op play like Red Dead Redemption / GTA 4 (You could kill each other in them, but that's based on player intentions, not the purposed aim of those games experience, especially RDR).
It's a mixed bag with the gaming industry, and implementing change is always controversial, so I see where you are coming from. But just keep in mind that developers are clever at dismissing our fears, because they're creative geniuses and do some amazing work that we weren't expecting to happen.
I'm pretty familiar with how a game company works, and production schedules, and budgets etcetera. About those that complain... people will always have opinions, and you can't please everyone, even if they were drawn into the hype or not, and possibly were one that fantasised beyond what was going to happen with the game up to release content, and/or took a journalists opinion rather than forming their own first. Each to their own basically.
Some developers pull multiplayer off, while others don't. For example:
Eidos with Assassins Creed: Brotherhood. It's not co-op (Like I'm implying with Skyrim), but it was an example of a single player game with added multi-player mode that was addictive, as it was fun. It worked so well that I would have paid extra just for a standalone version of the multiplayer, as playing with friends is always a great time for me. The move for AC:B worked out fantastically. I personally can't name any that haven't worked out well, because I don't like to bag on developers, as they deserve credit for their hard work.