Anytime I search for an addon via the search box in settings > add-ons manager I get all these theme results. Here is a search for "syntax" (via the add-ons manager) I had to make it very zoomed-out to fit long page into screen cap:
I use themes personally to visually differentiate between profiles. And I have nothing against fun and frivolous user customizations. Am not hating on the concept.
I am curious about why they are so aggressively pushed so that they show up be default when trying to search for add ons you need to toggle off every time. Searching for an add-on to do something and searching for a theme that has some keyword included seem to me like totally different tasks and mixing them up is a strange choice.
Is this like a major things firefox thinks people like about it? Do people like it?
Maybe just so new users realise they're a thing.
Firefox out of the box isn't very attractive, so mixing in themes by default maybe helps retain new people without driving us lot away.