They are all pop stars though, aside from the possible exception of Ed Sheerhan.
I think the pop audience has different expectations and the artists have a shorter life span. Good looks, good session musicians, hired song writers, big shows etc
The audience tends to be younger and have come to hear their favourite songs reproduced live.
Edit: They also have the financial backing to get the PR and prime time shows and media exposure. Clothes designers, make up artists, life coaches etc they are selling a lifestyle not just music IMO