"Adults" were busy pushing Harry Belefonte and other acts while the Beatles were withheld from an American audience.
The suits are clueless.
The lack of exposure to good/new/young music does not mean it doesn't exist.
There is most definitely some good music out there that doesn't get mainstream exposure. Radio is too highly formatted for some music to get a chance because it doesn't fit with in narrowly defined groups, and MTV rarely shows videos anymore and when it does it's even harder to find a rock band. The Drive By Truckers are a prime example of not fitting into a format, but being deserving of wide exposure and not getting it.