Welcome back oldgit... it's been a while
I agree that during BB1 and BB2, people weren't really in it for the fame as they didn't know what to expect from the experience - but all that has changed.
Channel4 and Endemol are here to make money, and to attract as many people to watch their show as possible. They know that the majority of people apply for the fame (there are exceptions like Jonathon this year) but they need to pick a group of people that a) are entertaining to watch and b) that viewers can relate too. Perhaps the characters do represent people which you see in the streets, but maybe thats the reason they were picked.
- Mark