The question is inherently incorrect! Evolution dictates the length of cats’ tails and evolution is always correct in the very long-term. Tails are functional and they have to be at a certain length in order to carry out the function for which they are designed. The function of the tail is to help provide balance to a cat, when help in balance is particularly required, which is when chasing and turning very quickly and when climbing and walking along precarious elevated locations. When a particular species of cat lives a life which requires more assistance in keeping balance, the tail is longer. Two very good examples come to mind.
RELATED: Which wild cat has the longest tail?
The longest tail of all cat species is on the snow leopard. Another very long tail relative to the size of the cat is found on the margay. The snow leopard often traverses 40° rocky and snowy slopes to attack blue sheep below. They live precarious lives on precarious slopes and when they chase prey animals they have to twist and turn. To keep their balance their tail acts as a counterweight. When the cheetah runs so quickly after prey and the prey animal is darting left to right the cheetah’s tail swings left and right as a counterbalance to help the cat keep their balance under the difficult and sharp manoeuvres.
As stated, the more a cat needs a tail as a balancing counterweight the longer the tail will be. This is the primary function of the tail. To summarise, the length of cats’ tails can neither be “so long” or “too long” because it is the product of the near perfect process of evolution as espoused by George Darwin. If it didn’t need to be long it wouldn’t be long and if it was too short it would, over eons, become longer.
When domestic cat tails are very short and sometimes non-existent as in the Manx, this is due to a distortion in the evolutionary process, which is due to spontaneous a genetic mutation in certain domestic and stray cats confined to an island population i.e. on the Isle of Man between Ireland and England. The mutated cats were allowed to survive I guess because they were protected on this island. Although a shortened tail does not severely jeopardise survival.
Any cat breed with a shortened tail, and there are a few (e.g. American bobtail), have them because of deliberate selective breeding (artificial selection) which works in an entirely different direction to nature’s evolution. Artificial selection is rapid, evolution is very slow. Although it can be speeded up under changes such as climate change.
The domestic cat’s tail also serves a purpose, probably a secondary purpose, as a signal of friendliness when two cats in a colony, who are friendly with each other, approach with an erect tail. This is called the tail-up position. The recipient of the visual signal knows that the cat is friendly.
RELATED: Cat Tail Types
Another secondary and non-useful consequence of having a tail is that it signals to others when a cat is in two minds about what to do. When a cat’s mind is flicking from one decision to another the tail follows. It is an attempt of the cat’s brain to try and get the cat into a decided situation and in doing so the tail helps to keep the cat’s mind, metaphorically speaking, in balance until the mind is made up. A wagging tail does not signal anger in my view. It might signal irritation but this is due to an unsettled mind.
Below are some more pages on the cat’s tail.