There’s two parts to it. Microsoft claims they need kernel level access to implement their paid for security product ( Windows defender while free for home use

There’s two parts to it. Microsoft claims they need kernel level access to implement their paid for security product ( Windows defender while free for home use is not free for enterprise ) If they firmly believe that, then they cannot block other software from having the same access or it would be anti trust. They could perhaps make it free and bundled in windows, but they don’t want to lose the enterprise funding.