There's one restaurant in my area that has some tables for one. I noticed that, for me, those do feel more complete when I'm dining alone. Instead of extra, conspicuously empty seats around the rest of the table, there's a table clearly designed for one diner to just enjoy a good meal.

And it's not enough to have tables with only one chair. If such a table is amidst larger-party tables, I think it still makes the other usual places at the table feel abnormally empty. What makes tables for one feel "right" has something to do with their placement in the restaurant (so as not to feel odd or exceptional), their orientation (so as not to face the diner towards someone else's gaze--unless mingling is the goal), and then the size and number of seats.

It's probably difficult for some restaurants to accommodate solo diners due to a need for density, but when a restaurant might have some space that would otherwise not be all that useful (like a little extra space between a planter divider and a walkway, where larger tables just wouldn't fit), it is an opportunity to attract solo diners who want to enjoy the solo experience of focusing on the meal and their own thoughts rather than bar seating. (And, on that topic, I think it's becoming more normal for people to not want alcohol displayed prominently in front of them when they're really just looking for a nice meal.)