They can't show kids underaged drinking on TV-period. For the risk that someone under 21 will drink and the potential disaster that will spell for CBS is
precisely the reason they haven't cast anyone that young (unless alcohol isn't an issue-which they can easily control).
There are also emotional/psychological development issues that prevent someone 18 or 19 from legitimately competing on that level with people much older. But still, it's the first reason that dominates the decision.
As far as why they are now casting people that age (if indeed they are), it's simple. The show will be dying soon. They've had two all star seasons and they've done all they can. Sure, the ratings are okay, but it's at the end of its road. Reality TV is at the end of its road for that matter. One last effort to attract a diminishing demographic.
Someone's been paying attention to TV audiences and have discovered that they need to attract college aged people once again. What better way than to actually cast college aged kids.
There are also emotional/psychological development issues that prevent someone 18 or 19 from legitimately competing on that level with people much older. But still, it's the first reason that dominates the decision.
As far as why they are now casting people that age (if indeed they are), it's simple. The show will be dying soon. They've had two all star seasons and they've done all they can. Sure, the ratings are okay, but it's at the end of its road. Reality TV is at the end of its road for that matter. One last effort to attract a diminishing demographic.
Someone's been paying attention to TV audiences and have discovered that they need to attract college aged people once again. What better way than to actually cast college aged kids.



