Because Turrddo Tax is for DIYers (nonprofessionals). ProSeries is for tax professionals.

If they screw the return up then they'll get a tax preparer with a Efin

I am now a DIYer since selling my practice.  I don't have an EFIN....so I am forced to use TurboTax or some other equivalent non professional program?

Yes. Or get an EFIN if you are eligible. But that takes weeks/months.

Or file on paper.

Thanks.  I am fine with filing on paper.  But as I assemble the 1065 to send in, I see a new AZ requirement  to efile.  Ugh...so I went ahead and sent in the extensions and filed a paper copy while I figure out efile.  Any recommendations re DIYer programs?  Do you know if ProSeries transfers to Turbo Tax?

I figured.  I remember going from TT to PS year ago, I guess it doesn't transfer the other way.  Oh well, the fixed asset entries will kill me.