Hence my using Gnucash over Quickbooks. It just works, they don't charge me to access my own data, and the interface is extremely stable.

Spend any amount of time talking to customers and you may find that many of them, maybe even most, don't want the responsibility of maintaining infrastructure. They want "insert money, get more software." The few that run their own infrastructure often come back to SaaS after realizing they made a monkey's paw wish. Many aren't ready for, or interested in, that level of involvement and responsibility. It's a burden, and the economies of scale available to software make marginal scaling more efficient when done by the provider. Not always, but it's often a perfect fit.

But only a bad salesman dictates what the customer needs— talk to your customers.