IAH Gate Waiting

Does anyone know why the gates are always full at IAH recently? The last 3 flights I’ve taken in the last 3 months have all arrived on time or early and then get assigned a gate 30+ min after sitting on the tarmac.

Is this a new workaround to the new Department of Transportation rule for airlines getting fined for 3+ hour delays? They just land in the destination “on time” or “early” to then just keep you waiting in the plane to solve the problem after you arrive?

This has happened with United all 3 times but my friend landed with American and got stuck waiting 4.5hrs last weekend. She also was not eligible for a refund as they “arrived on time” to the airport. This seems like an odd issue that’s happening very often now. I have another flight out of here this coming weekend again and will see.