I think it's rather unfair and misleading to say just about every animal coming to a property as a service animal is fake. @Lorna170
As you know you can ask vetting questions around what tasks the animal helps a guest with and we don't have to accept emotional support pets.
You can also have rules saying a service animal must be not be left at the property by itself.
There are many genuine owners of service animals who travel using short term rentals. But as you say there are a number of guests who will try to pretend they have a service animals but by no means the majority.