Pet fees are common. Sadly, many pet owners feel that their pet's poop is too good to pick up. Parks put out pet bags, they maintain dog runs, some go as far has having you sign a waver that if your pet poops and you don't pick it up you will be charged a fine or be evicted. Still, even at the nicest parks you can often find dog poop that has not yet been policed. Therefore, the park must give an employee the lovely job of picking up poop, they must fill the poop bag holders, rake the runs, and maintain extra liability insurance since they allow dogs on the property. Guess that is why we pay extra for each animal.
JMHO