The 747 was actually designed with this in mind from the get-go (hence the raised jumbo hump to allow front-nose loading), because the expectation was that they would not be in service very long until supersonic transports became the norm.

The A380 is just too heavy when empty to carry much freight. It was already a struggle to find engines that could fly the thing, and for airports to upgrade runways to deal with its weight.

Airports had to build new gates to service the A380. Ofcourse as it turns out very few routes can sustain 400-500 passengers. People want to fly directly to their destination- Amsterdam to Boston do not pass JFK.