Yes. Your OP said not from windows itself. Which is not true. The fact that Microsoft gave away Windows 10 has more to do with them pushing UWP and move users off of 8 ASAP (as Metro was abandoned, and the Windows Store is a key focal point for them) than anything.

Businesses still pay for Office. Users still pay for it. OEMs still pay for it on desktop machines. The free upgrades are over.

Yes. Revenue from Windows is down. People keep PCs for upwards of 5+ years these days. That wasn't the case in the 90s. Hardware was improving too fast to make that viable. Even software upgrades would obsolete old machines. That doesn't happen anymore - at least not nearly to the extent that it did back in the Windows 9x days.

Also, computer proliferation is very high now, so there are much less newcomers to the market. This is why PC sales are not that amazing.

Mobile device vendors are able to do what they do because they still have consumers on a fast track upgrade treadmill. People discard viable devices because they can finance a new one less than a year later.

If Carriers stopped financing, that market would stagnate as well. iPad sales are a good indication of that, in fact. People keep them for years before upgrading, because the contract prices are laughably high compared to smartphone upgrade plans and the wifi devices are bought outright.