Probably because the 1TB of storage you get with Microsoft 365 (or whatever it is called now) for <$100/year is more space than most computers come with. I’ve

Probably because the 1TB of storage you get with Microsoft 365 (or whatever it is called now) for <$100/year is more space than most computers come with. I’ve had OneDrive for a very long time, and there was a couple of years where they didn’t have the files on demand feature as they rewrote the OneDrive client. It was a major regression for me. If you don’t like that behavior, you can always just check the box to sync everything. I do that on my machine that has 2TB of storage.