Bitcoins have been over a couple of hundred dollars for more than 5 years now. Kids can only get so many by mining. Don't imagine too many teenagers have 10+ bitcoins without family help in getting them.
Bitcoin is maturing, and so are its holders.
Alts are probably a different story
Well I don't see any chances teenagers could have 1 bitcoin and above. They can't work to have one except if they have rich parents. Title should be changed to 'People with most bitcoin should be at least 20 years old. It is pretty possible and some 20+ year olds are really interested in cryptocurrency especially in bitcoin.