I know my own taxes pretty well. I don’t follow the tax code changes but could fill out a 1040 form on my own. Even did for a short time.

I use tax prep software because I do NOT want to worry whether I copied the amount from line C to line K correctly. The IRS forms are a nightmare!

The postscript in PDF should allow something more sane than what we have today in IRS forms, but that’s just wishful thinking.

I use to think that. I'm capable of putting numbers in a form correctly. A good tax preparer can point out things like "did you know that your specific commuting pattern entitles you to claim mileage?", or "the law says the way you have your working environment set up at home means you can deduct some of your utility bills", and so on ad infinitum.

Basically, unless you get someone who has a deep knowledge of the law, if your tax situation is non-trivial (see my post above this) then you might be leaving money on the table. It's a terrible, idea to evade taxes. It's a fantastic idea to realize when you're paying more than you're legally required to so that you can fix it.

The IRS's fillable forms do a perfectly fine job of copying values around and doing the basic arithmetic that they can automate.

No, that's Intuit lobbying.