I think there's several different underlying causes to Windows feeling more secure (not needing antivirus) these days:

1. Security on desktops has been improved quite a bit. You can no longer simply email someone a .exe file that's the equivalent of `sudo rm -rf /` and have it work, multiple levels of safeguards (from the browser, to the email virus scan to windows defender catch it). OS's also simply won't run unsigned binaries anymore unless you force them to which is (maybe?) a good thing.

2. Piracy has been on a downtick, and people seem to be more open to paying for software since App stores made it somewhat more acceptable. Less likelihood that people download sketchy binaries off the internet and run them on their PCs.

3. More hours spent on mobile OSes which are inherently more secure. casual PC usage at home is declining.