What is the point to lvl up?

I have been randomly playing this APP game on my phone. Only because they take most Anime characters and merged them in to a card game. My question would be do they need a license for this? Or all these artwork can be used for their game? I have seen a lot of fan art in this game as well. 

As pretty as this game can be and with all your favorite character, even from yaoi and game character, the whole game feel lack of content. You can't do anything but to make your cards stronger, pvp or do event. There is no story line whatsoever.
I'm just there for the looks o3o!