Back in the 1960's this is what a mobile phone looked like.
Obviously its got a dial phone, for the obvious reasons that if you stepped on uneven surfaces, or chewing gum, you wouldn't want to be accidentally phoning people or running up costly toll bills.
These were also emergent days for feminism. The problem was that while it was really hard on socks, it was an impractical device for women. Agent 99 had far too much to do in her working life to risk getting holes in her tights, in these olden days, getting holes, or runs, meant darning.
An additional problem, was that walking around with one shoe off was worse for women, the heel difference made this an impractical lopsided choice. Furthermore, the innovation developed at a time when stilettos were the fashion choice for female fashion victims, this made accidental tympanoplasty and self imbedded grommets a frightening surgical risk, especially without anaesthesia.
Then there was the social stigma attached, these were not very enlightened times regarding mental health issues, talking into ones shoe, in public, could have got you certified.
Amazing really that it ever caught on. Who would have thought That Get Smart a spy spoof would lead to the ubiquitous use of mobile phones that we have today.
Amazing also is that the phone is more memorable than the dialogue, this was 1965, there was a cold war (the war that you have when your not having a war) and remember this predated the pre-emptive strikes on weapons of mass destruction occurring 40 years later...
The dialogue between Maxwell Smart and Agent 99 in the episode titled Appointment in Sahara. Behind the two characters is an image of a mushroom cloud:
99: Oh, Max what a terrible weapon of destruction.
Smart: Yes. You know, China, Russia, and France should outlaw all nuclear weapons. We should insist upon it.
99: What if they don't, Max?
Smart: Then we may have to blast them. That's the only way to keep peace in the world.