In some cases they may use other applications that simply aren’t available on macOS, and don’t have any comparable option on macOS.
This is why I have both a MBP and a PC Laptop.
An important application (to me) doesn’t exist on macOS (and never will, per the developer - and it’s a pretty huge company) and the F/OSS alternative (which works well) also isn’t available on macOS because it heavily utilizes .NET Framework and Windows APIs and they say they aren’t porting it over (they’d basically have to rewrite the entire thing).
Some people need their computers for more than a single task/usage scenario.
When someone asks me for a recommendation like this, the very first question I ask is “What do you want to do with it?” and “What software can you not live without?”
With Boot Camp not being a thing on M-Series, it’s muddied the waters a bit, as well. Before, I would just Boot Camp windows onto the Mac and switch based on what I needed. Now, I literally need two separate laptops (or to eschew Mac altogether).