They are increasing access to markets for the average person. They're also encouraging uninformed investment decision-making by doing things like sending push notifications when big name stocks swing way up or down, earning money by selling users' trading data to the highest bidder (increasing the overall fraction of "national product" that ends up in the pockets of financiers as the purchasers of that data make fast moves on that info) , plus that whole debacle with their "checking & savings" product.
