Spin-offs for much loved (or much hated) side characters are a long and noble tradition. Honey Boo Boo, for example, became a far bigger pop culture icon and Internet meme than the child beauty pageant show she started from. Frasier, too, was on TV long after the newest generation of viewers forgot about Cheers. If these contestants made enough of an impression, good or bad, the producers might as well earn more views out of them.
Contestants eliminated from The Bachelor should not be allowed on television or Hulu again. They really ought to be sent to ranch in Wyoming to work until their have bruises on their hands and wrinkles from squinting into the wind. The never ending procession of lazy spin-off television shows is what prevents entertainment from coming up with a truly new approach and engaging content.
Not every contestant in The Bachelor is interesting enough to have their own reality show. Granted, the final contestant goes onto the next season of The Bachelorette, and that works fine. That's where it ends at though. If contestants start getting their own shows following being eliminated I doubt there'd be much a show given that most of the time the reason they got eliminated is because they're not interesting enough.
Eliminated contestants from The Bachelor should not go on to have their own reality TV shows because the bulk of the reality show content has already been displayed on The Bachelor. In addition, the extra reality shows may steal the spotlight from what it is the actual show: The Bachelor.