In fact, in the vision of 2015 in Back to the Future Part II, there is a cut to someone using a phone booth. Most people around now wouldn’t even remember how to use a payphone, and a lot of the kids of today probably don’t even know what they are. This idea of the filmmakers that people would still be commonly using fixed line telephones will have made it impossible for them to think of something like the smartphone. In addition to that, the film didn’t even have the internet! Yes, there was a video call between future Marty McFly and his boss (see video above), but the service provider was US Telco AT&T. McFly also received the “You’re Fired” note via fax (a very relevant piece of tech at the time). One of the main facets of the smartphone is its internet capabilities.
Not only did ‘80s era sci-fi fail to predict a few major inventions, they also got a few wrong as well. Unfortunately, there are no hoverboards or self-tying shoelaces yet, but it's possible they definitely still could someday.