I don't know why it gets recommended so often, I don't actually think many people use it, but for some reason it's brought up all the time. I blame Distrowatch.
I was an MX user. It looks nice out of the box (better than Mint at the time) and the "flagship" version runs smooth on old laptops, probably thanks to Xfce.
Side note, MX has a rare feature, it provides a choice between two init systems.