The main problem with this theory is that Microsoft is absolutely abysmal at user end security, and they always have been. Frankly, they do not understand the issue.
But, more to the point, the whole TPM/secure boot stuff is a compromise; originally (I think this was about the time of Vista), they partnered with OEMs to have them include a DRM chip that made it literally impossible to install any non-windows OS on your laptop. They've managed to still get an implementation of TPM that makes switching your OS too confusing/difficult for the average user.
Anyway, bottom line is they only care about money, and they neither care or even understand the security needs of the end user.