However, Apple chooses not to do this unless they can establish that it is actually your device. Giving trade-in credit for activation locked devices would effectively be giving thieves an easy way to make money off of these otherwise useless devices, so they don't do that to avoid incentivizing theft.
It would be cool if Apple offered a program where these activation locked devices could be returned to Apple for free. Apple could contact the last known owner and let them know their device has been recovered. If Apple doesn't hear back from them, then they could wipe the device and sell it as refurbished, or recycle it (depending on how damaged it is). This avoids creating an incentive for thieves to steal, but also overcomes the e-waste argument.