That's exactly what I'm talking about. Especially in the case of a product that had revenue/customers, I can't see why you'd want to quit just to go get a job. Sure you'll make some money and your work may have a larger scope to impact, but why not be known as that awesome company that makes awesome things?
If my memory serves me right, a startup that builds apps to improve the experience of a pre-existing service doesn't stay for long as an awesome company that makes awesome things. It usually either plateaus out or gets gobbled up eventually.