Some things are fun in a group. Some things are fun alone. And something things are just unpleasant without the company of others.
An online research site polled nearly one thousand of its users about things people find painful when flying solo. Here's a look (those polled could list multiple answers):
9. Eating at a ramen restaurant alone: 1.9 percent
8. Traveling alone: 2 percent
7. Seeing a movie alone: 2.3 percent
6. Going to a concert alone: 6.4 percent
4. Going to karaoke alone: 13.3 percent
4. Going to a bar alone: 13.3 percent
3. Going to a buffet alone: 21.5 percent
2. Going to a yakiniku (BBQ) restaurant alone: 23.4 percent
1. Going to an amusement park alone: 53.7 percent
As the poll reflects, being asked "A table for one?" is generally seen as somewhat sad when going to places people usually go with their friends, family, or loved ones. Ramen restaurants are often (though, not always) places businessmen quickly grab lunch or dinner, so many people are more used to going to these types of restaurants by themselves.
Recently, there's been a trend to make certain kinds of solo activities less depressing, such as karaoke places that specialize in serving customers who want to sing alone.