There is a lot of competition between dApps, and I think the two more important things dApps (and any other cryptocurrency) must do correctly to become popular are being innovative and make a succesful marketing campaign.

The original airdrop of EOSJacks is probably what allowed this cryptocurrency to get so much volume. To sustain its grow it is important to keep focusing at marketing, develop new games to the platform and convince other gambling sites to accept EOSJacks currency.

I also noticed from other comments that it is not very user-friendly for users that haven´t used EOS before, and that is a problem that should be fixed as soon as possible to attract more users.