This was developed mostly for computer chess, where games are often played starting from preset positions, where one side already has a significant advantage. The top chess engines, when playing each other from the regular starting position, which is very equal, will almost always draw (especially in time controls where they have an increment of one second or more), so we humans have to force them to play lines that they would never go into so that the games aren't all draws (and while some games can be exciting and still drawn, that is not the case with most of the lines the engines will pick when playing from the start position).
This is essentially just a subset of the Chess960 positions that don't require any modification to the castling rule.
This is essentially just a subset of the Chess960 positions that don't require any modification to the castling rule.