We do have some heroes.
I see plenty of little kids, oing the Mayweather shell, even more hooking the bag with a huge grunt and many kids actually refusing to smile (in an attempt to be like Cotto!)

Every person in boxing picks their own hero or idol. In the 80's these feelings may have been heightened as peole had the same favourites (Duran Hagler Hearns and Leonard.)
It just so happens that today the "great" fighters are more dispersed among the weight divisions and don't appear in the same conversations as Leonard Hagler Hearns and Duran would have. So it's not that boxing's heroes have faded, it's just that they're competition may have.

Also ppv contributes.