The bigger the Prize money, the more "ordinary" people will enter, and of course, the contest will become more vicious.
If the Winner were to just become a recluse, the Media would venomously accuse them of being "snooty" "elitist" and "aloof", and they would thus be hated by the public.
Also, for all the criticism of "wannabes", many on these forums would feel disapointed and baffled if a BB Contestant didn't seize the opportunity to forge a new career and leave a dull job; the word "stupid" would be used frequently.
How many singers started off as waitresses? (Madonna, Cyndi Lauper, Vanessa Carlton, etc).
How many actors accidentally became actors? (Harrison Ford, Helena Bonham Carter, etc).
What's wrong with trying to create luck instead of waiting for it?