While I do agree with the general sentiment, that it probably is what a normies want, but then the cynic inside me wakes up.
Preloads are not there to make the service or experience better. Preloads are there, because someone paid for them to be there. So someone makes money on them, doesn't care exactly what they are, and is selling your attention and your time to get there.
So no popularity numbers needed, only a good offer.
Could it be MS has stats from MS Store to actually see what users install (say I have WhatsApp from the Store, among several others, not mentioning Office). We don't have numbers from the telemetry, but they have, so we guess, but they may actually know. Not something unrealistic for me.
As side note, I find astonishing things, for good or bad, when looking out of my nerdy bubble.