I think of Lubuntu as Ubuntu (just a different desktop), and Ubuntu is not all I use as I use Debian & Ubuntu somewhat equally.
I’m no fan of GNOME; yes it’s functional & I can use it efficiently for a day or sometimes a couple of days before I’m pulling my hair our; so whilst it’s installed on my system, I only rarely use it (a change is as good as a holiday?).
I’m a lover of multiple desktops, so as already mentioned this box has GNOME installed on it; Lubuntu’s LXQt, but also Xubuntu’s Xfce. I love Xfce too. My Lubuntu/LXQt desktop is made up to match my Xfce one, so it’s easy for me to forget which I’m using (the WM themes the easiest give away)
Why Lubuntu/LXQt - it’s light, efficient & stays out of my way, letting me do what I need to do.
Xfce does that too, and GNOME can on occasion (as in ‘stay out of my way’, GNOME isn’t light & even modern Xfce isn’t as light as it was though it’s not too bad when using GTK3 apps) but I find it regularly getting in the way (thus the hair pulling). I could use MATE or KDE too, but again I’m back to pulling my hair out every so often (which I can’t keep doing!) thus I stick where it just works for me.
FYI: This is a 2009 dell desktop; so a light desktop is somewhat important. Yes I’ve got newer boxes (with noiser video fans), but Lubuntu is light enough I can use this box that I’d prefer and not lose out.
I’m probably using Ubuntu 70% of the time (and that’s mostly Lubuntu); but I’m using GNU/Linux 100% of the time