I think Simple would get a lot more attention then they are getting if they offered a paid service for people who wanted to link their accounts and use their platform as a money tracking tool.
Simple on the other hand is pretty useless to me. The rates are awful and it's just a nice looking app - really don't get it. But suppose I don't fit the use case they pivoted to before launch since I don't set budgets and more just keep tabs on when money comes in or out. Will probably end up closing my account there but your idea of becoming more like Mint (linking accounts) could make it useful.