There are some games that don’t work or don’t work as well. Some anti-cheat systems don’t work but the website protondb.com will tell you how compatible specific games are. For some people that’s a deal breaker and that’s ok, hopefully as adoption increases the situation will get better. I was disappointed to find out that vermintide 2 doesn’t work for example.
I have no idea on the pirating side.
I think that’s because they don’t understand or don’t care about the risks. Annoyingly I was in the process of making my own version of this campaign when it launched but I was aiming to explain why someone should care that the os is no longer supported and why its a problem first, then suggesting what to do about it. Options weren’t exclusively Linux but I realise buying a new device isn’t always an option either so some people will absolutely keep using 10. It’s not about getting to 100%, just enough that you can make a difference or keep devices out of landfill.