Bear in mind that Unreal and Unity have, I imagine, pretty large teams working on them. Panda doesn’t: it has a fairly small group of developers.
That said, it’s not as though no work has been done–as you yourself noted, while cumbersome and incomplete, it is possible to deploy somewhat to Android.
(Also, I think that Android support at least is actually on the roadmap–but I’m not sure that the roadmap that I found is still current and intended to be seen.)
I think that the following threads show the most-recently reported state of deployment on Android and iOS, respectively: