Furthermore, it also has to do with the current trends in zoo education and animal welfare. One current school of thought in the ambassador animal world has been moving away from touch opportunities with ambassador animals. Part of this is related to disease transmission (ex. reducing risk of the animals getting COVID-19), while part of this is related to what sorts of educational messaging is the zoo trying to achieve (ex. some zoos like to stress that this animal does not make a good pet, and touch opportunities can debatably undermine that messaging).
The debate about COVID transmission is not one I'm prepared to dive into, thanks, but as far as messaging is concerned -- I'm glad you qualified the idea of touch opportunities undermining the 'pet' factor as debatable. While I think this may be true in some cases (lemurs come immediately to mind), it's easy for the zoo involved to give examples of why the animals involved don't make good pets. Touch opportunities don't get in the way of that, to my mind; They just make the zoo involved dig deeper for good examples on why the contact experience is so unique and should never be duplicated outside a legitimate zoo. The better the example, the stronger the message.
In the realm of animal welfare, many zoos are also moving towards having encounters be voluntary for the animal, in order to increase animal choice (which is important for good mental well-being). Due to this, these zoos may look more critically as to how the animals respond to touch opportunities, and while some animals may love the attention/being pet, many others do not like these sorts of opportunities.
You'll get no argument from me on this. I'm all for voluntary participation on the animal's part. My biggest wish is for zoos to be more open to the idea of interaction if the animal(s) they're looking at show signs that it's something they want to do.
Regrettably, the idea of animal choice in this context is not one which I think has found wide acceptance.