Why is that? Why not pay some money for a good product and support the developer? Why does everything need to be free or open source?
A good question. Here is my take on it:
1) Price. $59 dollars can buy more than 10 beers around here!
2) Alternatives. We have so many high quality, cross-platform, well supported, Free and Open Source alternatives.
3) Sustainability. Over the past decades I have seen plenty of projects become unsustainable because tools they used became unavailable or were not available for some new OS or platform. Perhaps the vendor goes away. Perhaps they stop development and support. Poof! Huge amounts of time, money and effort suddenly become useless.
See the end of Eltech's ExaGear or the slow death of FLASH for recent examples.
There have been many more over the course of computing history. Back in the day many used Intel's PL/M language on their microprocessor projects. Which Intel dropped a long time ago and never provided for their newer processors anyway.
4) Collaboration. If there are bugs in the product people can't fix them. If they have enhancements people can't do anything. I'm unlikely to be able to fix compiler/interpreter bugs anyway but I'm loath to even spend time creating bug reports for commercial projects. That's working for someone else for free. I'd rather donate my time to the community of an open source project.
5) Security. We don't know what goes on in a closed source binary only executables.
6) Transparency. Sometimes one want to "open the hood" and see how something is put together. Perhaps just to learn something. Perhaps to see how it can be fixed/extended/ported. All kind of reasons.
7) Community. When I publish code openly I'd like it to be usable by as many people as possible. Better that it is not required for them to also spend money to make use of it. Better they don't have to have the same platform as the me. Better that it does not impart to them all the disadvantages of close source systems listed above. I have no significant Open Source projects but there are people who have been grateful for my little demos, examples, and so on.
8) Licensing. Often closed source products have very restrictive conditions about how and where their code can be used.
I could go on...
Some of the above may seem may seem fanatically philosophical or even religious. Some crazy people see it as "communist". I don't. Most of the reasons I give have very practical and economic reasons for being. The actual monetary price of a copy is not even the main point.
I think you are conflating some separate issues in your question. The "free" in Free and Open Source software does not imply free of cost. It does not imply developers don't get paid. Likely most Open Source software is developed by employed professionals getting paid by the likes of RedHat, IBM, Apple, Microsoft, Google, Facebook, and countless others. Companies have realized that an open development community for tools they use is a good thing, they pool their efforts and expense.
Anyway, it's up to you. It's not my concern what you pay for and use. I have no problem with lone developers attempting to monetize their efforts. I only point out the potential problems for you.