Cyanogen may be better for the end user, especially the technically savvy end user, but the metric of success for manufacturers' Android variants are a mixture of end user experience and other factors like brand differentiation. It's possible that they're achieving exactly what they're trying to, which basically boils down to being able to produce an ad that shows off the features that their phones have that their competitors' Android phones don't. Once the sale is made it doesn't matter too much how awesome the user experience is or isn't.