I feel like it's not that good for the animals, especially with Children grabbing them. Touch tanks are a very American thing, and they're really not found that often in Europe
I somewhat agree with you.Many touch tanks are barren pools,sometimes even without any substrate.And fish that show signs that they are negatively affected by the human contact,like always being in the far back of the tank should be relocated to another tank.But some species actually seem to like the human contact from what i have seen.
I know sharks and rays can be very affectionate sometimes, other fish too. But I don't think it's worth the stress of the other fish to have a touch tank.
Partially also because of greasy hands, which is undoubtable bad for the health of the fish and the water quality