because firefoxOS is no longer under development. /e/ probably doesn't want to take over development of the whole operating system.
also, there is no easy way to collect all FOSS apps available for firefoxOS, because firefox didn't track that information. that is, if the market is even still running.
the goal of /e/ was to start with a fully functional system, and remove the bad bits one by one. lineageOS and f-droid make that easy.
developing firefoxOS would be more like starting empty, and having to develop or port any apps needed to make it good.
Successors to Firefox OS, like B2G and KaiOS are still being developed. The app situation is more of a problem. Web apps are a partial, if imperfect, answer to that.
There's a KaiOS flip phone being sold in the US. As Alcatel Go/Alcatel Quickflip.
It's really really bad. I have one. Like, the basic experience is just bad. Even for a flip phone. There is also no supported way to install apps or anything, even though KaiOS theoretically supports this. I had intended to see if I could find a back channel way to even write my own apps and install them, but the basic experience is so bad I lost interest.
also, there is no easy way to collect all FOSS apps available for firefoxOS, because firefox didn't track that information. that is, if the market is even still running.
the goal of /e/ was to start with a fully functional system, and remove the bad bits one by one. lineageOS and f-droid make that easy.
developing firefoxOS would be more like starting empty, and having to develop or port any apps needed to make it good.