The motivation is money. If you don't use Edge they won't be able to track the web sites you visit so they can sell your data to advertisers. Google does it too with Chrome. That's why if you visit Google sites with a non-Chrome browser they will push you to use Chrome.
Apologies if these are naive questions, but why does Microsoft require use of Edge to track user data? Can't they obtain data from the DNS requests any browser makes to access websites?
And are there any ways to mitigate the amount of data they obtain when using Edge (e.g. Ublock)?