First, it is an absolutely unnatural thing for a cat to do. Expecting cats to do things as humans do is going just too far. Second, toilet seats are slick and slippery even for young children, so think what it must be like for a cat. There is always a chance of a cat slipping and falling, possibly injuring himself in the process. This could also be an experience that will frighten the cat enough that he will refuse to use the toilet again.
Toilets also require that the cat jump up .
We provide hand-grips in public restrooms and our homes' bathrooms for our elderly and infirm humans. Third, toilet training a cat also makes it impossible to see the urine output, which is important in monitoring the cat's health . A cat who has a urinary tract infection may not feel comfortable trying to balance on the toilet seat when he is already miserable from painful urination or an inflammed bladder. He will more than likely seek out other spots in which to eliminate. Feces can't be checked accurately if there is a possible problem, as the water in the toilet will change the feces' consistency.