I don't know what devil you are representing? The assertion is that you can buy a new 4G phone today and get booted off their network for using it because it is not on a list of phone models they sold.
I can also buy a brand "new" telegraph today from Amazon for $10. Should carriers still support something that was created 100 years ago?
Very few people are advocating that they keep 3G around using 5x5MHz of spectrum for little gain; people are just advocating that they not limit consumers from using the supported device of their choice regardless of whether it's on the list.
[0] https://www.att.com/idpassets/images/support/pdf/Devices-Wor...
No one is saying ATT should continue operating their 3G network. On what grounds are they terminating subscriptions?
Also, there's more than just Apple/Samsung/Google. Operators are shutting off 3G, but keeping 2G alive for a while longer for crap that's abundant, and doesn't need anything more anyway.