Probably many people would be happy just using an open source version of Photoshopp 6 an they would be ok missing some of the features released in the last 10 years (like painting 3D surfaces or automatically fill a region of the picture that you delete). Sometimes companies forcing you to update your software to get your money it's not a good thing (Windows 10?). With open source there is always the chance of forking as what happened with OpenOffice and LibreOffice.

The issue of having to pay to get access to your tool it's a big issue.

For big companies having to pay for 100 workstations yearly the monetary incentive is big.

Once many people is aware that in the long term it's a better deal to put their money into software libre projects, maybe different companies could compite to get your money.

> they would be ok missing some of the features released in the last 10 years (like painting 3D surfaces or automatically fill a region of the picture that you delete)

Content aware fill was in Gimp before Photoshop. It was an open-source PhD project.

Photoshop version 2 was given away for free on the adobe site a year or so ago. It works great and does most things fine.