The thing is, when you have the one player you open up the game more for out of the box thinking and lots of pre-planning. A solo character won't just charge into the orc den, they will find a way to poison their water supply, redirect a river, enrage a rabid troll or some other way to deal with them. It leads to a lot more "combat as war" moments when straight up encounters are not advisable. It also allows you to play in ways that are interesting but would not be in a full group, e.g. assassinating the slaver stronghold one by one over the course of a few days. This would be very dull for all the non-assassin players in a group environment, but works perfectly for a solo game.