Area code was likely all the same, maybe 2-3 tops, and associated both with the following exchange and geography, and used extensively.
Exchange, also likely all the same, maybe 6 at most, and again likely associated with geography.
https://www.kcbd.com/2021/10/12/new-10-digit-dialing-procedu...
Note the date on this: Oct 2021!
> Starting on Monday, October 25, 2021, Texans with phone numbers in the 254, 361, 409, 806, 830, 915 and 940 area codes must dial 10-digits (area code + telephone number) for all local calls.
The average person doesn't even have ten good friends, much less a need to memorize dozens of phone numbers. They would buy address books / contact books to write down dozens of numbers, not memorize numbers they very rarely use.
Most of the time, local networked IPs all start with the same values for the first 3 octets (maybe 2 if VLAN but then usually only one digit diff). The same was true for most people's local phone number memorized registry. Those of us old enough, we only had to dial 5 digits using (70s) the last number of the prefix before eventually moving to 7 digits to include the full prefix (80s). The world suddenly changed when we had to dial the entire area code as well (90s).
