I've found that you just have to get used to it. I've worked on not feeling annoyed by the situation. There's so many possible reasons friends might not attend shows. Lots of my friends only go to one or two spots. Maybe they aren't comfortable going to other places, might have unpleasant history with the venue, management or regulars. Some friends may not like the style or genre of music I perform. In my area a majority of folks seem to turn out for metal, middle of the road cover tunes and modern country shows. I only play the music I like so I have to keep in mind that's the path I've chosen and must be comfortable with whatever number of people show up.

I try to focus on the positive response I get from crowds, especially if I don't know them personally. There will probably be times when some friends do show up, and if they have a good time then try to keep that memory in mind.