Kattapa is a devoted slave of the Mahishmati kingdom and a skillful fighter. The ancestors of Kattapa first swore allegiance and fidelity to the Mahismati kings.

Everyone born into his family must serve as a slave to the throne, according to a promise made by his forebears.

Kattapa had kept his forefathers words and was a loyal slave to the throne till end. Due to being the slave to the Throne he had to carry out all the terrible tasks that the king wanted him to do, including killing Bahubali, who he loved dearly.

However, it is repeatedly demonstrated in the movie that Kattapa was against the system of someone being a slave, whether it be to a good monarch or a bad one.

So just for breaking the pledge set by his ancestors he did not marry or have a child that had to become slave of the throne.