I have said this before. Weights are to keep fights fair. Divisions are to keep some kind of order and make 'champions' possible. The second is more arbitrary. Hate it all you want. It won't change. OH. Almost forgot. Sometimes catch weights are just to avoid abc fees.
That's a 33 lb difference but Pac vs any welter at 147 will be worse because he started at 106 lb thus a difference of 42 lbs.
Cotto-Pac will happen at a catch weight. If Cotto wants money, he will fight at 144. I hate the idea of that happening, but money talks.