The ERC20 tokens are the ones which are usually used by day trader due to their high volatility and drastic fluctuations which means those are the tokens which will always have high demand in the market.
Now that Coinbase has accepted most ERC20 tokens to be available to be traded at the exchange platform that will attract most of the traders towards them and bringing it closer to greater milestones making it the choice of most of the traders.
Just a nice marketing strategy.