Nobody wants them. The only reason I have an iPad mini 2 is because I gave my dad my Wi-Fi iPad Air 2 when I upgraded to the cellular version and nobody really wanted his mini. I'm glad because I actually kind of like to take the mini out with me sometimes because I can store it in my pockets if I have to.
Most of my devices are just old devices that I still use sometimes, so no one really wants them, like a Galaxy Tab Pro 8.4, Moto X 2013, iPhone 5s, and Nexus 4.
I'm sure there are schools or charities that will take them. Sorry for sounding preachy, but an old device that means nothing to you could mean the world to a young student whose family can't afford even a used one.