The problem with Britney/Gagz/Beyonce is their over-reliance on Pop and their failure to target other demographics. Pop is always embracing and accepting new trends, and just because you're a perceived "superstar", doesn't mean you are exempt from being given a "no ma'am.
That is why Kelly Clarkson, P!nk and Adele may not be in the spotlight but their albums ALWAYS sell because they target the Adult Contemporary stations (k not Kelly but u get my drift)