At least the way spectrum is currently allocated, there is only so much to go around. In order to deploy stuff on the newer technologies, the old must be retired.

In the US, at least, AT&T is planning to sunset most of their 2G by the end of 2016. T-Mobile is planning to keep some 2G going until the end of 2020, Verizon is aiming at 2021 before they sunset 2G and 3G. It's not really about consumers, but M2M communications that don't really need fast speeds (and replacement costs are expensive).

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