The requirement of Photoshop and Excel often comes from integrating to someone else's work. This someone could be in your team, in your company, an external collaborator, a state or government representative, a customer. Or a friend, or family.

Adobe tools are the only ones supported for both digital collaboration and print. It is not a simple question of whether it can open PSD files, or support the same editing tools and operations. In many cases, it absolutely has to get the correct colours on paper, Pantone or not. And not just paper, cardboard and canvas, too. And any exported PSD must open correctly in recipient's Photoshop, including layers and whatnot, not just colours.

When finance sends you an Excel file and you open it in Calc, and some of the personnel costs columns values from macros look a bit off, how do you know if they are? Does the $1k/month macro package run correctly on Calc? Does it run at all?

(I don't mean that Photoshop or Excel get these things always right, either. Sure there are many situations when the replacement is good enough, I use the open source variants exclusively. But when things go wrong, you can actually blame the tools as long as everyone uses the same ones. If you use a different tool than others, you really can't blame the tool, you'll be asked to switch. And other people quite possibly will blame you. And you might lose a contract or money, or both.)

For most people, it makes more sense to learn the industry tools, not the free copycats. This is unfortunate, but I don't see it changing. The network effect is too strong.

For most people, especially the target audience of the article, it makes sense to at least try. Most people don't match Pantone colors or deal with $1k/month macro packages.

All of those are great.. but let's be honest.. they services they are replacing are way way way slicker and easier to use.