Imo, I believe it is to facilitate/brake down of the moves for teaching purposes. I personally never formally took ballet so I can never remember the "positions" names like 5th, 2nd and 1st. I also think it's to bring belly dance into a more acceptable dance form instead of a "seedy" dance form like so many people (general public, some like to call it) think it is. Jazz dance has "jazz 1st", and "jazz 2nd", which came from ballet terms, so I think the terms for belly dance should be "sharque (sp?) 1st" and so on.