hey, i was wondering why the melodic scale is different ascending from when its descending, what is the reason for this?

And diminished scale either begin on a semitone or a whole tone dont they? Could anyone explain why please?

thank people
The melodic minor is different so composers can do different things with harmony. So for example, the III chord in a melodic minor could either be major or augmented because the 6th note can be different. It's just more options for harmony and melody.

And with the two diminished scales... I dunno, that's just the way it is