Because it comes from marketing strategy and marketing campaigns. Toy Story, Cars and Nemo all have in park experiences, so from a marketing point of view, they are the ones which have the main marketing budget allocated to them. Its also to to with market saturation and public awareness. I know it sounds unbelievable, but there would still be people who go to Disney parks and stay at the Disney hotels who would not have
Disney+. So from a business and marketing perspective you would not use an IP only available to a small segment of your customers.
The same with A Bugs Life. That marketing campaign is over, due to the area being rethemed to Avengers Campus. No one is going to allocate budget to theme a hotel area to an IP that has been removed from the park.