99% users won't ever need that. For cases when they do, they can find guides, modify settings or install software that does what they want.
This is not an excuse. What they are doing is unethical.
People don't need an excuse. They play their games and that's it.
it contains binary blobs without the source code
Any distro you download can do this exact thing and you wouldn't know for a long period, unless you spend enough time to compile the whole thing yourself, compare and research.
I was explaining to you how DRM works and why it's wrong
I consider myself knowledgeable but you surely chose a wrong example to teach people about DRM. Try some denuvo or eac maybe.
If you buy a Windows laptop, you can install any operating system on it too. That doesn't make Windows ethical.
Whatever that means, users don't care about it. Compared to others, Valve provides a lot more value in most of their solutions. They are hackable just enough to satisfy most enthusiasts.