Gemini's app appears to charge higher fees than the regular portal which seems rather screwed up to me also it only offers you market orders.
More incentive for people to use that exchange through their phone's web browser rather than their app. 
I couldn't imagine trading on a phone. You need precision and access to more information than one small screen can provide, but then I am old.
Most people don't care about any of that with how they buy in low to sell high based on nothing but their own gut feelings. In that case it's perfectly suitable. Robinhood app is mobile too, and it's being used by millions of average joes to trade stocks and whatnot wherever they are. It all comes down to user demand, and there is plenty of that.The more advanced traders use their mobile phones mainly to manage their positions on the go rather than to actually trade.
