In my experience building the product for my company, FareHarbor, what you describe -- steady growth driven by ever-improving software and hard-working sales --

In my experience building the product for my company, FareHarbor, what you describe -- steady growth driven by ever-improving software and hard-working sales -- is more familiar. (This is in the SaaS / SMB world). We launched with just enough features to serve a single client. For a while, each new client needed something more. After something like a year we were able to onboard some new clients without changing anything about the software -- that's when I felt confident we were onto something. Nevertheless we didn't suddenly experience a deluge of customers, phones ringing off the hook. Perhaps sales got easier, onboarding got easier, people had heard of us already. But even as we were growing by several times each year, we were still "slogging it out", doing the work.