Because there is no official release, the community has taken matters into their own hands.
When Papers, Please exploded in popularity in 2013, the question of a handheld port was raised frequently. Lucas Pope expressed interest but noted technical hurdles. The game was built in a specific engine (Haxe/OpenFL) that didn't have native support for the 3DS. Papers Please 3ds Port
If you’re interested in exploring this further, I can help you with: Finding the for the 3DS Comparing the Vita vs. Mobile versions Instructions on how to mod your 3DS safely to run fan ports Because there is no official release, the community