30 years ago? Your basing your comment on when the parks didn't event have the Mummy ride..let alone Potter/Simpsons land
USH can for sure work without APs but all these companies want MAX profits and to do that you need Aps in some form, you need to be able to sell special treats, preview Nintendo merch and or do updates on the park to get people hyped to come. Thats all for Aps not normal people coming over to ride the studio tour