is there a fundamental problem with singlehanded distance racing? How much safer are two people than one?

One man fall off boat, other man come fetch. Small problem when other man not there.

Just kidding - I`m sure that a boat sailed solo, with all the appropriate safety measures, would be just as "safe".
In a recent Lake Malawi distance event (700km race) the skipper of a boat fell overboard, the boat capsized, and the crew couldn`t right it. They were found many hours later, and the lost skipper was no more than 500metres from the boat. So what makes 2up safer than solo ?