I think what many fail to realize is that to the OEMs, those custom UIs are part of their branding. Samsung doesn't care if you want an Android phone, they want you to want a
Samsung phone. They use their custom UI to change the look and feel of the UI as well add their own special features (whether or not those features are actually useful are up for debate) -- it is what is meant to set their phones apart from the competition, whether that competition be Apple making iOS device or HTC making Android devices.
Notice on the S3 commercials that ran so much recently, they focus almost exclusively on features that part of Touchwiz and things unique to the S3, but never really mention any common Android features at all (even if they are awesome).
I wouldn't either because some of the Touchwiz features are what makes Galaxies so awesome and unique. I would however, love them to improve the "look" of Touchwiz. It can look a bit cartoonish at times.
Tom
Sent from my Nexus 7 using Tapatalk HD
This quote above is a perfect example of my point -- a person who recognizes that the features of TouchWiz are exclusive to Samsung phones -- and a person who has a positive experience with one brand is more likely to buy that brand again.
FWIW, I actually don't think that recent versions are TW are that "cartoonish" at all (since ICS), but I did feel that way about some their older iterations.
I also used to think that Sense was by and large the best OEM UI out there...but since then it seems like HTC has gotten lazy and failed to really improve it at the rate of it's competitors, and could be a reason why they aren't the cream of the Android crop any more.
Whether you like them, hate them, or are just willing to tolerate them, the custom UIs aren't going anywhere for a while, because the OEMs have no reason at all to want to get rid of them. I personally love Nexus devices and have owned a few of them; I also love my Galaxy S3 (it helps that I'm rooted and can do what I want with it). I'm not trying to argue whether stock Android is better or not, I'm just sharing my 2? on why I don't think it matters to the OEMs what we think.