The other answers address the history here better than I ever good, but I wanted to point out one example I hadn't seen mentioned.
https://en.wikipedia.org/wiki/Area_code_917
917 was originally a mobile only area code overlay in New York City. For reasons that are unclear to me, after that experiment it was decided that the US would never do that again.
The FCC found in 1999 that service-specific overlays are "unreasonably discriminatory and anti-competitive." I gather the thinking at the time was that 917 was full of pagers, voice mail, and car phones, while "real" phones were in 212. Times have changed and they're now prepared to approve an overlay in Connecticut that would cover the whole state, both area codes 203 and 860, with the new area code used for services that are not location specific, for which they give mobile phones and Onstar as examples. R's, John