Well I will just mention that i am an iMac user since 2007 and I replying to your message with Win 10 via Bootcamp. Mac gamers choose the bootcamp route because its an easy solution and gives access to more games and software. I am willing to bet that Mac gamers are at least 8% if not more. Bootcamp became popular way before Steam did and way before we saw the big switch of big Game studio from pure Windows to Windows/MacOS. Windows also has a notorious reputaiton of being far more stable on bootcamp that a regular pc and and its a reputation that my personal experience confirms it. Because I am a developer I have decided to stick with Win 10 and bootcamp and it has been a smooth ride so far but from time to time I go back to MacOS. Windows 10 also has been the first reliable OS that came from Microsoft.
Of course bootcamp is not the only solution, there is also wine like solution and vm solution but Bootcamp is by far the most popular for gaming.
Another reason to stick with bootcamp is that games may offer a MacOS support but are not quick to fix bugs and resolve issues usually becayse they develop on windows and use crossplatform APIs to port to MacOS using Windows and not MacOS devs which can cause all sort of issues that can take time to resolve.
Of course bootcamp is not the only solution, there is also wine like solution and vm solution but Bootcamp is by far the most popular for gaming.
Another reason to stick with bootcamp is that games may offer a MacOS support but are not quick to fix bugs and resolve issues usually becayse they develop on windows and use crossplatform APIs to port to MacOS using Windows and not MacOS devs which can cause all sort of issues that can take time to resolve.