FEAR, thats the word.
In my case it is for other reasons (check rxtools thread page 103), but developers have fear of dont find any new exploit to have fun with. The most powerful actual exploits (beside Ninjhax) where found by the Gateway TEAM (they have many hidden hacks since 2012, check OOT save for details) and they have fear of dont be able to find any new exploits. In other words "they are ***** in their pants"
but anyway, thats good for now (check my opinion of why at rxtools thread page 103)
Legal trouble is a valid fear tbh, especially after geohot and the PS3, and especially now with the ESA trying to remove the fair use clause from digital software in the DMCA. Removing fair use from digital software and protection circumvention would make all 3DS hacking illegal because it would technically be bypassing their set restrictions they placed, piracy or no piracy. I definitely wouldn't want to risk legal trouble over something that's just a hobby for myself.