Various reasons.
Free software tends to be the Johnny come lately of the field, or if it is earlier it tends to be forked off as a paid closed thing and only when that achieves dominance does someone pick up and run with the older one.
Paid and closed tends to make for a budget as well which does support (being able to phone up someone that does this task for a living is better than having to have in house options either dedicated or hoping your IT guy does it as well as everything else). Depending upon the business then historically free software does not play nicely with business IT (network installs, network permissions and all the rest).
Creative fields also tend to evolve from needing a basically a supercomputer (kind of seeing it now with AI) to something mortals can use. As open source tends not to have a budget or indeed supercomputers (though there are notable exceptions) then you also have that to catch up on.
Schools tend to then get given software (and support) knowing that they will teach it and thus have the people go out into the world and both use it/demand it/expect it and companies might not care about $1000 a chair software if it is basically a rounding error and they can drop in and start working vs having to learn new software (which might not be as a capable, as stable or as supported both by the company and the world at large if you have to send it out for other work). Schools also get to say they teach industry standard software and techniques (while most creatives are less concerned with percentage in industry at 1 year from graduation than many others it is still a thing).
This all repeats for many years. The company that makes it gets big. At that point their last real competitor which maybe only hung on for this time, or a competitor seriously funds the open source aspect, or maybe a government that needs accountability that closed can not provide (though that is also tricky -- most major governments probably have windows source code and office source code if they want it for just those reasons), maybe gets donated to the open source world. Said now basically monopoly probably gets bloated, gets silly ideas like charging a yearly fee, stops listening to the little guys, a big company with only a tangential use (some people make websites in photoshop for instance) and supercomputer becomes nerd level gaming PC instead so said nerd (which maybe also did it for a living or as a minor hobby while at school, and possibly could make a youtube career using it) also wants in but $1000 a year is a bit steep and the open source eventually steps up.