Why I cannot pair iPod Nano with iPhone?

I have iPod nano as primary device for listening to the music. During excersize I am using headset connected to it. What would be great is to be able to pair iPhone to iPod and, during a call, to answer on iPod. Another use case would be: headphones are attached to iPhones, which is paired to iPod nano, and I am able to listen to the music that is on iPod.

Answer to trivial question: Why I am not listening to the music from iPhone is the fact that I have 5c model with 16GB and the amount of free memory for the music is not sufficient to store all songs currently on iPod.

Curently those two devices cannot be paired at all. Answers found to similar questions were simple: No or Why would you need this etc. Such answers does not gives any useful information since there must be clear reason why these devices cannot be paired espacially since both made by Apple.

PS

Not to mention that I may pair iPod with Windows 10 desktop PC. Could it be also true for new Lumia devices? It souds awful but this is just for proof of concept.