My understanding from the research we've been able to do is that there were a few issues:
- The branding was weird. TurboTax is supposed to be about DIY, so having a tax pro service under that was confusing. I spoke to several former preparers with Personal Pro who said they would get clients asking for technical support with TurboTax
- It started as "intrapreneurship" within Intuit, so it was a small team trying to grow it (not a top-down initiative). I suspect they had certain (large) targets they couldn't meet that were gates along the development process.
- I suspect ultimately, similar to above, it never became large enough to be interesting to Intuit, and it was likely cannibalizing some of their existing customers as it was.
[1] - https://www.taxaroo.com