I play on PC. Really hard to get anyone in the lobby at all. Even if I host, I will rarely find someone who joins. And after 5 minutes of waiting with me, they'll usually leave to probably have more fun than waiting in a half empty lobby. 
Well, good for you that you have a choice in the matter. I wouldn't either. 
I agree with you. However, it's a shame that this big rift exists between perilous and nightmare. Wish there were more average players (like me) that played it regularly.
These are my issues of not PUGGING NM
1. I get disconnected or frozen very often and in PUG games I can not return to the game . Other players may take my place or I may not know anyone in the PUG to return.
2. NM is still very in demand because of completing the challenges and the higher xp for my high level friends
3. NM is still popular for other high level friends for the Hakkon Weapons
4. 2 and 3 means in my private games (sometimes I will start public for lobby but go private) are fill up very fast or I join my friends lobby
5. PUGGING yields player who really shouldn't be at NM and are even challenged to be in perilous who die within seconds and spam come here for revival when I am the only who can solo in the group
6. PUGGING yields average players who come in die often and when I carry them for 4 or 5 runs they get a Hakkon weapons the talkative PUG doesn't say a word and just leaves after the game
7. With that said I typically P{UG perilous and if I find a group who is well coordinated and will accept positive input then I will ask them if they want to go to NM, switch to private and do the run
I suppose others who do NM runs often share some of my feelings. Whether they do or not, it is the way I am currently running NM