I dive alone frequently. It’s that, or not dive except on the weekends. Not many people can just go diving any day during the week when they want to. Most people have jobs, kids, etc.
None of the charter boats I know of around here will allow solo divers, but I got my own boat, so I don’t need to concern myself with their rules.
Over the last 15 years I haven’t had any real crisis pop up, just some inconveniences. I didn’t wet the strap on my BCD one time before I put the tank on, so my tank floated off midway a dive on the rock jetty. It was kind of funny. At the time I owned with a red AL80. It’s pretty common to find stuff at Radio Island that other divers have lost. I’ve found goggles, found a great flashlight lying on the reef, found a titanium dive knife once. So I’m goofing around the rock jetty checking out all the cool stuff and out of the corner of my eye I see some motion and look over. It’s a red AL80 Scuba tank. I thought "Wow. Someone lost a tank. And it looks just like mine! How awesome, now I have TWO and they’re just alike. What are the odds of that?".....about that time the tank floats far enough away in the current and starts pulling on the reg in my mouth. Then I realized why it looked just like mine.
Another time I had a fin strap break. The tide was going out so the fin got away and went on with the current before I could grab it. I had to swim back with one fin against a pretty stiff outgoing tide.