I guess it's a marketing thing.Lumina is also a bunch of nasty "Qt stuff", also it is not even a DE, what "Lumina" is:
fluxbox+compton+some Qt applications, panels and pop-up windows.
With Lumina, TrueOS can boast an "own, integrated" desktop, be a "real operating system", that is "different" from FreeBSD, and allegedly "better" to people for who the DE is "the computer".
Regarding herrbischoff's comments, I have been thinking a while.
Today's desktops involve much more than programmers.
Today artists and psychologists are the actual "leaders" in desktop shaping.
I guess Apple's and Microsoft's payroll budgets only for artists and psychologists working on GUI design is by orders of magnitude bigger than the whole FreeBSD.org's budget.
In this perspective, Lumina, which looks like "programmer art", represents a GUI evolvement stage of before Windows 3.0.