Everything from the marketing to branding/design to distribution channel is designed to encourage higher frequency active trading among retail investors. When you're using Facebook-like product design tactics to encourage "engagement" (in this case, more trades), then you're not a neutral fee-free brokerage but an active contributor to irrational behavior.

I would be less critical if they had a library of investor education materials, or required investors to go through a training course to understand the risks of riskier trades (i.e. margin or options trading), but as far as I know they don't have anything like that.