Initially curiosity is what drew me to it (that and the name sounded super cool)
The two primary things I do on a computer are 1. Development and 2. Gaming. Initially I wanted to see how these worked out on a system that was immutable. So, I saw it as a sort of challenge. But then I rapidly (within the first few hours/days) fell in love.
Keeping a clean system while still being able to muck about is awesome. I can spin up a toolbox and play around with some new tooling with different versions and just dump the toolbox when I’m done with it. Though now days I mostly have 1 primary toolbox that I have a lot of stuff just piled into 
Gaming is simple with things like Steam and Itch.io, but some games require more libs or features like Wine. For these I can make custom launch scripts that just exec toolbox run wine someWineGame.exe or a native toolbox run someGame to use the libs inside my toolbox and somewhat containerize said games.
Development is also extremely simple. Since I mostly use Java I don’t really need the toolbox, since I can use java with all my local libs and such in a Java folder in my home directory. But I did finally put NetBeans in a toolbox in order to integrate with SceneBuilder (which is also in a toolbox).
Once I figured out a little how to use toolbox and then the rest of my normal applications (Fractal, Gedit, etc…) I just use as Flatpaks I really see no reason to not use Silverblue. I feel safe, and more confident when mucking about with programming, and I don’t feel like I’m cluttering up my system for an eventual reinstall.
It just feels right 
And hopefully once we can get the Fedora on Mobile (PinePhone, Librem5 etc…) more stable and in a better “final” state, we can start to make that into a similar immutable ostree system.