Doge coin deserves it because it's a old crypto coin now, I think as old as BTC if I'm correct,
In my opinion if how old the project means nothing right now. The fact that if coinbase was adding dogecoin caused by it has a very big daily trade volume and coinbase didn't wanna try miss the opportunity to get big volume from the dogecoin traders.
Even if it doesn't have utility usage and it's not a problem for coinbase consider this company was aiming for the huge daily trade volume of doge coin