The Department of Justice does maintain an archive of cases it has settled with businesses and one thing you’ll notice is that a lot of venues do go years without being challenged. Whenever there are media stories about people who sue for violations this also often comes up as its usually about some small business being required to make expansive changes years after they first built out their business. And this typically relates to the design standards where there is a set of freely available, published requirements and resources available that have existed for decades now. (It’s amazing how many non-complaint restrooms are out there!)
Operational violations are able to go on for even longer because those regulations are not as clearly defined and decisions aren’t going through third parties like an architect or building department that are supposed to be reviewing for compliance (and building departments don’t always check!). As your patient and several posters here have demonstrated there are plenty of people willing to just provide documentation. It’s something they are okay with so it’s not challenged. Anyone looking to challenge an operational policy is looking at a minimum of months if not years before there is a resolution through the Department of Justice, a state agency or lawsuit. For something like event tickets the event is going to be long over by the time there is any enforcement. People deal with it and just move on, which is in a lot of ways still the societal expectation.
The lawsuit against Six Flags has only occurred in the last few months despite the system existing for years at over a dozen parks across the country. And even that suit seems to have been triggered more by multiple rouge attraction employees than it was the system alone. Even with a large venue, mobility accommodations are roughly pegged at about 2% so a lot of enforcement really is a bit of a needle in a haystack.