Everyone is guitly of this. Everyone is guilty of having certain expectations of their favorite artists. Here's an illustration. Say, for some reason, Steve Vai was bored of writing the same old guitar-driven albums and wanted to try something different. Say he decided to do a rock album along the lines of Nickelback or Creed with a heavy emphasis on vocal arrangements and nearly no guitar work. We (or fans of Vai) would be angry. We want to hear his guitar work. Hell, that's what he's famous for. But, from his standpoint, it is very possible he was just bored of working on guitar stuff and wanted to try something different.
This notion of 'selling out' is very strong in our society, but it's not necessarily the case. An artist may just want to experiment in different musical genres, with little or no concern about an album's success or monetary value.
Could those of you who are Michael Angelo fans still respect him if he suddenly decided to perform 3-chord pop songs and tour with Britney Spears as her guitarist? Worse yet, what if his decision was not driven by financial gain or stardom but rather just an inherent craving to start playing simple pop tunes?
I think that artists are very much labelled and are expected to stick to those labels.