Not the person you're asking, but I've been a Simple user since 2016.

When I started, I was diligenty using the savings goals. I had a goal for a car, a house down payment, cell phone upgrade, etc.

Eventually as my account and goals grew, I found it to be stupid to leave so much uninvested. I just kept a mental note to keep my balance at around $15-20k, transferred everything else to my brokerage.