I then went and found out how many folks one of our competitors (a bit more mass market than us) had writing payroll software.
The answer was it was a six person team just to keep up with the government changes every year. We never bothered any more with that idea.
Payroll is surprisingly hard.
The new company I switched to did not allow me to do payroll on the days that I'd wanted. They only offered 2 or 3 options, none of which matched what I'd done before. "That's all we offer" was the reply. There've been a couple other 'restrictions' (lost flexibility) on some behaviors - nothing horrible, of course.
I've no doubt removing some of that flexibility has reduced their overhead - there's enough changing regulations every year in multiple jurisdictions - keeping the main stuff under their control as simple as possible seems to have worked out for them. I've had... 4 years with them without incident, but 2 years of pain with QB before.
FWIW, QB hosed up dealing with my state. Federal was fine, but they created so many problems with my state filings...