My guess would be that they needed instant updates. Rick had said that MSStore took days to publish updates, IIRC.

1. The store version has a limit on the number of computers - not that I am currently close to the limit, but I don't like it. 2. Not updated fast enough. 3. I want to keep my Microsoft Account separate from my Work account on my work laptop, and I don't want to create a Microsoft Account for work.