The consumer licensing of the OS isn't their cash cow, the subscription revenue from tied services is, so changing the OS base doesn't change the subscription push.
A very small portion of the market is even aware a Windows license costs money. If they've bought a Windows PC since 7 it's pushed them for free all the way to 11 and the vast majority don't build their own to find out they need a license (and heck it really doesn't do much against you if you don't buy the license these days anyways).
The real money in the consumer side is in the services and data, O365/teams/onedrive/bing/edge(browsing), which is why they push these so hard on default installs. It wouldn't matter if they used Linux as a base, their push would still be to push users towards these services.
That a few people who even know what Linux is would be more likely to use thire services if they stopped pushing them to the average user isn't going to sound enticing to Microsoft as they'd be losing a lot more than gaining.