Because when you're born into that life, there are obligations, whether you like it or not. Yes, at this moment, he's sixth in line, but you really never know what could happen. The Queen is in her 90s and could pass at any time. Anything could happen to Charles, anything could happen to William, and Wills' children would be too young to assume the throne, so it would go to Harry. Yes, there's little chance of that, but there's still a chance. We're talking centuries of tradition here that they are bucking, and IMHO, the loss of traditions is a big cause of the breakdown of society. Also, they are not celebrities. They are Royals, and monetizing on that while shunning your ancestral duties is in extremely poor taste.