Cats do weird things you cant explain....take for example i have 2 cats that lick table legs and one of those cats likes to eat toilet paper and kleenex? What is the purpose of that? The other scratches the wall (declawed) by his food dish & likes to eat plastic. My cats are weirdly awesome..lol
Pets are just plain crazy!! My dog doesn't really drink water like one would expect.....but if I take him on a walk and it's raining, he can't help but try and drink out of every puddle in his path. COOKOO!!
Dirty dish, or a dog has been drinking out of it and he/she feels it's contaminated, he smells something off with his water or he just likes the freshness of the faucet and the taste of the toilet water.
The running water is colder and fresher than stale water that has been sitting in a bowl. My sister has a fountain that is designed for cats who like running water. It is aerated and I think that might enhance the flavor.
My kitten does this too. Cats like running water. They sell dishes with a small fountain for under $40. Keeps the cat drinking and away from sink most of the time. My cat has figured out how to turn on the water in the sink. It's cute.
Your cat would lick water out of the sink and bath tub over its water dish because it may become bored of the regular water dish, so it decides to look for fascinating ways of drinking water. I hope this helps!
The truth is very simple and will hopefully demystify this once and for all. Cats, just like humans, need something very special, SALT. Most shampoos, conditioners, and bar soap, as well as the human body, carry an abundance of this precious and hard to find in nature mineral. Once the cat has learned where it can get it, the memory will always be hard wired into its brain, much like how some african apes, such as the bonobo, will find natural salt reserves near a small body of water and retain the knowledge of its whereabouts for its entire life. After consideration of this you will find that is is almost unfathomable that we humans would ever eat a meal without sodium. The same goes for every mammal on earth. They all crave salt. And wherever they can possibly get a taste, they will, including the bathtub floor. Remember, salt is also a very important vehicle for proteins and other vitamins to for even distribution in the blood. It is also important for retaining water to stave off dehydration.