People use Photoshop for sheer capability, not for the layout, naming conventions and shortcuts.
er.. no - I've been a daily user of Photoshop since '98 or so, but after getting annoyed with Adobe's subscription model a few years back I bought Affinity Photo and looked to move over entirely to that, yet I ended up back in Photoshop purely because of literal decades of muscle memory meant that every interaction that I had with Affinity's offering came with an undesirable cognitive speedbump.
I'm not a fan of Gimp (haven't given it a shot in over a decade, to be fair) but if it covers the basic capabilities of PS and provides for an almost straight swap for users looking to change, then it is literally the layout and shortcuts that will be the decider for them.
Some people do. I know my way around Photoshop very well, but do not use any advanced features. I tried using GIMP once and bounced off immediately, trying to do what I knew how to do in Photoshop was very hard, the learning curve felt very steep.
These days I use Photopea which meets my needs perfectly (but is not free software).
I'm pretty sure 95% of photoshop users only use a feature subset thats also available in GIMP (except for maybe the latest generative infill)
Although that is true, moving to a different application with different layout, naming conventions, and shortcuts is difficult. That is the use case this project addresses.
I don't think it's contentious to say that the user interface is a huge part of using a program.
But if you don't have the money for a photoshop license, learned photoshop, and don't want to pirate, this is a good middle ground.
Photopea is also a good solution
Time to bring back again the (true) story of when I was working at uni and they were looking for another graphic designer to join our team. Boss told us one of the candidates refused to do the test because the computer didn't have Photoshop installed. All they needed to do with an image editor was to crop an image.
I really think most people use Photoshop for the same reason they use Windows - they don't really know/they don't want to learn anything else.