Still, what's your motivation for wanting to grow more? Money can be a legitimate motivation, but you said that's not it. I guess I'm curious what drives you now.
I believe they mean that by, increasing your user base and revenue even more, you'll convince Stripe that having their own feature/app developed is absolutely necessary. And they might be concerned that you represent a one-person company, single point of failure. They can't just rely on you to be there for them forever.
But I really hope they don't :)
Great story. Thank you for sharing and for the inspiration.