Hi, cofounder of Simple here.

Some people are driven to change banks because of interest rates, but those people are not the majority. Most people change banks around major life events: moving, getting married, getting your first job, etc. Or, they change banks when they have an extremely negative experience with their current bank.

Either way, changing banks is a hassle, and we really have to make it easy and compelling. But interest/rewards aren't the only motivation, or even the primary motivation, for switching one's bank according to bank industry research.