I'm in New York City. I do not see this.
I see single people use their phone while they wait for their date/friends to arrive. Or while their date uses the restroom.
I see groups of friends where one person is temporarily texting because the babysitter reached out, or a friend is asking where they are, etc.
Going to restaurants and bars is expensive. People aren't going out to use their phones.
NYC here too, I'm not sure where you're going but go to any sports or Irish bar and >50% of the people there will be on their phone, especially when they're solo. I do wish I could read a book, but so many bars keep it so dark even in the daytime that it's impossible these days.
People go out by themselves all the time (I'm single, WFH and live by myself, if I didn't go out by myself I would literally leave the house only once or twice a week).