Microsoft has done phenomenal getting even more businesses to adopt O365/Teams/Outlook. And while I’m sure there are plenty of people out there who use MS/Outlook for a personal email account, I just don’t know any of them. Outlook is for work amongst the people I know. (You don’t choose it, it is chosen for you).
As far as more ads in Outlook, more and more of the online world is becoming one giant advertisement with a lengthy amount of personal data to know what you can be enticed to buy. The stuff outside the ad? That’s the content you came to actually see