I think the issue is Bob, simply familiarity. People want something new, not the same old, same old.
We're very different from most people. We don't just go to one theme park, once a year and ride each ride maybe once.
We got to multiple parks, multiple times and ride the same coasters over and over.
For most customers, they've been riding Nemesis for almost 20 years now. Okay, they've probably only been on it that number of times, but that's fine. If they wanted to ride on it more, then they'd go to the park more often. They don't, so they've "been there, got the tee-shirt".
air and Rita are "new technology". For people only going to the park once a year, they're still new rides. How many launches did you go on before they became a bit dull? How long did it take you to reach a real opinion about Rita? Probably about the same amount as most people have ridden it, if they've been every year to Alton for their annual trip.
This is why parks need to keep adding, almost "no matter what". The public get bored much quicker that we do, despite not riding as often as we do.
On top of that, parks need to try and make their new ride "special". Alton is particularly vulnerable to this, as it's set a precedent. Yet, there's not as much scope now for something new, and Alton are very tightly limited. Hence we end up with mixed bags like Thirteen.