This is a great thread. It's good to know so many others splurge for onsite for the same reasons.
When people say 'Disney Bubble' I picture obsessive Disney fans with customized matching vacation t-shirts (although I know this is becoming more common these days

), Tinkerbelle tattoos, and floor-to-ceiling Mickey Mouse paraphernalia in their living rooms. Nothing against those people at all -- I know there are plenty here and I am in no way in position to judge anyone for their hobbies and interests -- but when people talk of the 'bubble' it's easy to think, 'that's not really me.'
We stay onsite for the exact reasons others are describing. The resorts are so nice and so tied in with the overall theming and feel of the vacation. Port Orleans is a great example. It's a moderate resort with more impressive scenery and vibe than any luxury hotel I've ever stayed. It's stunning how immersive it is. But I can totally understand how someone more specifically interested in the parks would find it insane to pay $300/night for a motel room.
As others are saying, the reasons for staying on site are there. It's just a question of how much they can push the cost and reduce perks before it crosses the line. I'm planning a trip for October. I looked at Universal's website and resorts today. I've never done that before today.