I dont think that in the 60s-90s anyone would have necessarily anticipated the existence of smartphones as they are now. Rather than it being a “deliberate” choice not to have them in the show. Its just not a futuristic idea of communication that existed at the time. Theres not smartphones in The Jetsons either. Earlier ideas of what the future would be like were a lot more utopian than the dystopian hellscape induced by smartphones and social media. Their various ideas of the future were a modification of the way people actually lived then, which was simultaneously less connected but also more interpersonally social. They dreamed of a more connected future, but not one where that level of connection would rip apart established social fabrics