Why do cats have bumpy tongues?

So that they can get water in their mouth and lick hair and flesh off animals. The hard part is made up of the molecules in your fingernails. That is what makes their tongue hard, also as hard as your fingernails!

Cats use their tongues as natural combsCats use their tongues as a comb to maintain their fur. On the rough and humid surface the hair sticks well and is combed out with ease. On the other hand allows the rough surface then to release the hair easier in order to swallow it.

C. K. Tenge

Amsterdam
Cats have rough tongues for two reasons. Firstly, they act as grooming tools, separating fur much like a brush and keeping their coats nice and sleek. Secondly, their rough tongues enable them to lap up liquids such as water or milk (and cats shouldn't really be given milk; many cats are lactose intolerant and therefore cannot handle ingesting milk).
Cats have rough tongues for two reasons. Firstly, they act as grooming tools, separating fur much like a brush and keeping their coats nice and sleek. Secondly, their rough tongues enable them to lap up liquids such as water or milk (and cats shouldn't really be given milk; many cats are lactose intolerant and therefore cannot handle ingesting milk).