Reality is, there are still driver issues on older hardware (especially laptops) with Windows 10. Some of my friends get random hangs since upgrading. My grandma's sister had her laptop upgraded and can't find anything anymore.
It's a huge download and a huge change in how your computer works. This is not something you should just force on your users by tricking them to install it. Nudges and prompts are fine by me. Pushing it as an opt-out thing you have to actively cancel is just awful.