My parent's number growing was initially 77099, though it later became 577099 when the numbering system was tinkered with to allow for growth and efficiency at the exchanges. This was only as far back as the 90s, and such short numbers still work for landline-to-landline calls today. I don't have a landline, and if I did I'm not home enough for it to be a useful way o get hold of me. My numbers now are 11 digits, not as easy to drum into the head of a kid I expect (I don't speak from direct experience: child-free and planning to stay that way, but I know many people with kids at various ages).
OK, technically my parent's number was 10 digits rather than 5 because it was <areacode>577099, but that didn't matter as I'd almost always be local to that code, and if not could state my home town if talking to an adult who was doing the calling (or if I'd dialled the operator number, which I'd need to do anyway for a revere-charges call) and they'd know that bit.
We didn't need an area code for much of the time I was growing up in the 90s in the Atlanta area. It was a huge media thing when we got a new code and finally had to start thinking about it. We had an area code (404) but nobody used it until that pesky 770 (1995) complicated life for some, and 678 (1998) later messed it up for everyone.
