Titles are a fun incentive to do something besides get stronger.

While they hold no extra "power," it's a reward for generally being the top 3 at something in the game on your server. It makes you feel good to know that of all the people playing, your one of the best at something.

Aside from that explanation, pure bragging rights over other people. For example, "Strongest Power" between multiple p2w players is basically a daily challenge of who has the bigger bank account.