Why you should use Lubuntu is entirely your own discretion. Just try a few distros in e.g. VirtualBox, and come to a conclusion which one is fit for you.
I just happen to like the way the LXQt-desktop works. Lubuntu gives me a stable, nicely polished implementation of that desktop. Also important for me, Lubuntu/LXQt runs fine on older hardware.
Some twentyfive years ago, besides Windows, I’ve been using mostly Red Hat, Slackware and Gentoo based Linux systems. I can hardly remember the names of the different desktops I’ve used. What I do remember is that none of those desktops appealed to me. That only Windows had support for my semi professional sound card was another important factor for staying on that platform.
Around the year 2010 I got frustrated with Windows when my new and cheap laptop (“Designed for Windows XP”) started underperforming after a Windows update. After I’d installed Ubuntu 10.10 the world changed for me.
Finally a free and polished distribution had arrived that was perfect for my laptop and my needs. It took not long before my sound card got proper support, and I stopped using Windows at home completely.
After reading about Lubuntu, which had claims to perform better on older PC’s with less memory and CPU power, I changed my laptop to Lubuntu. And yes, it was more agile than Ubuntu. At first, I was not so keen on the Lubuntu user experience, but I got used to it.
Now I really love Lubuntu. In fact - I did not know that at first - it turned out that I love Lubuntu’s implementation of LXDE.
Several years ago I had some worries what would happen with ‘my beloved Lubuntu’ when the migration of LXDE to LXQt was announced. It turned out well. In fact, the migration has made the user experience even better.
The Lubuntu team deliver a great desktop, and I hope to be using their distribution for many years to come. It seems that stability of their product is important for the team. More important than quick implementation of the latest LXQt version. Personally I think that is a good thing.
Recently I am developing more and more worries about the direction Canonical is going with Ubuntu. I read 'TRG’s post about ‘snap’ etc. So far, the impact seems to be limited. At least, not more dangerous than what data other corporations already collect about me. However, I would like to be able to confirm myself what compiled software is supposed to do, by reading the source code, line for line. Or at least have trust in a group of people who have verified that for me. That’s the whole idea, and I think ‘snap’ gives that away.
Long time ago, around 2000, I, the end user of a Gentoo system, had in fact the choice: or download compiled packages, or compile packages myself. In fact, it was possible to build and install a whole Gentoo system from scratch. Well, it took ages (or say days), but I used to do that. I kept on doing so in the noughts, before I gave up on Linux and refocussed on Windows (for said reason, not for the compile time effort).
Well, to round up. In my opinion is open source software (and its implementation) all about choices. For now I like Ubuntu and the LXQt desktop on Lubuntu. I can’t thank the teams of the LXQt project, and of Lubuntu and Ubuntu enough for that.
Luckily, for me and you, we all have the freedom to make a choice out of several excellent desktops (all in their own right great), and several excellent Linux distributions (also all in their own right great).
At the end of the day, it is our choice. For now I stick with Lubuntu because I like the interface and the underlying Ubunty suits me.
Who knows what will happen in the future.