Dogecoin has successfully gotten the attention of the world, people are zealously pumping money into the coin and no exchange wants to be left out. The joke of the past has become most desirable and I'm not surprised that Coinbase has finally decided to add the coin.
Is about the American market and making money for coinbase, especially when the coin seem not have any legal defect that could drag the exchange in the future. Most exchanges are likely to be late to list Dogecoin, as a meme that long term traders in the space may not consider or hold any more. I feel meme coins like Dogecoin with strong community may be here for longer time than we expect.