They don’t assume we have unlimited money, they assume they’ll make enough sales to justify making it (and paying all the people who made it).
Yeah, some companies are making ridiculous profits and underpaying staff. This isn’t some pro-capitalism comment.
Taking things off of streaming platforms or not making old stuff otherwise available usually boils down to bureaucracy and legal stuff. Certain people need to be paid, or have the right to veto their content being sold, or stuff like that sometimes. And sometimes the companies have a legal obligation to either protect their IP or ensure things stay “offline”.
I don’t like it, but I know it’s not always simple.
If you have some sort of decent antivirus/antimalware like Malwarebytes, that would work for standalone applications to an extent.
Browser extensions are a lot harder to check.
Always make sure you get the RIGHT extension from the PROPER SOURCE. Same with most downloads and app store stuff on your mobile devices, but at least with executables, you can additionally run virus scans for some peace of mind.
Some tips…
I believe you can generally trust what permissions an extension or app needs (since the browser/device knows which permission an extension/app uses, and locks them away otherwise), but be wary of the implications of some of them (such as data from other websites, or accessibility features).