[Thunderbolt Android Development] JFMFT:
To expand on this, I'll say the following: Manufacturers are to hardware as carriers are to wireless service. Just as carriers (Verizon Wireless, for example) think it's more profitable to be more than just a dumb pipe wireless service provider (meaning they don't JUST provide your wireless service, but also sell you goods like accessories, VCast apps, etc.), manufacturers want to be more than "dumb hardware vendors" - that is, a manufacturer such as Motorola thinks it's more profitable to offer something MORE than just hardware. They HONESTLY (and sadly mistakenly) believe that their "innovation" (quoted because no one honestly believes they actually innovate in anything software-related) via Motoblur and other OEM custom skins will allow them to be unique in the hardware manufacturing space. Sure, they'll be unique(ly crappy). Pretty much everyone I know says their (insert Droid, HTC phone, or other Android device) is nice, but is a little laggy and needs a better battery. Take away the crappy skins and stock Android will ALWAYS provide better battery life and out-perform the custom skins like TouchWiz, Motoblur, etc.

I honestly believe if Google could get away with it and not fear for the immediate death of Android by OEM abandonment, Google would mandate vanilla/stock Android for all new devices ala the Nexus One/S/Xoom devices. But they know the sh**storm they'd incur from OEMs as a result of that policy/action being taken. In fact, such a decision (for all we know) could infringe upon and void contracts Google has with said OEMs. In order to get the big manufacturers on board (such as LG, Motorola, Samsung, HTC, etc.) they had to throw the OEM's a bone that would allow them to differentiate among one another. Unfortunately for the end-user, that means a sea of varying OEM-customized skins and layers placed atop Android's already sleek (as of Gingerbread/Honeycomb) and intuitive base UI. And let's be honest - I can't think of a SINGLE skin (aside from CyanogenMod, which isn't a skin but a heavy customization of the base Android AOSP UI/code that doesn't take away or change for the worse Android in anyway) that is "innovative" or "better" than stock Android. There are small ways each skin adds things that are valuable and useful, but much of that could just be packaged into the stock ROM specific to the manufacturer's device.

As sad as it is, custom skins and superfluous, laggy, bloated software additions by OEMs and carriers are not Google's fault, really - how else were they to get these people to take a big risk on Android?

I have faith that the market will prevail and true, vanilla, "stock" Android will be seen as something that is so good there's not really room for it to be improved upon, and manufacturers will (some day) drop their custom skins, at least for the most part. Then again, it may not happen - I can't imagine the millions, if not collective billions that OEMs have spent developing, promoting, and advertising their horrible skins. That's too much of an investment to set aside... after all, OEMs and carriers want to see the fruits of their labors grow and be nourished for all they can be. And until that happens, we're probably fighting a losing battle. And if it appears to carriers/OEMs that their efforts to bog-down and bloat Android are working and making them money, then there'll be no incentive to stop the trend. =/