It's not about visually plzing it's about efficiency. I want to be able to extract every possible xP point from every move. And since sweet scent is rarely a move used inside battle, I want to be efficient with my pp usage..
I know and I'm explaining where a 5 -> 4 buff is more likely and easier then a buff to the pp of it. One is hard coded into the game with set values. The other is reading that hardcoded data and saying 'hey if you see this move performing this action take 5 from that move'
TL'DR: think about it like this. You have a plate of 32 cookies that you and your best friend are gonna eat. It's alot easier to tell your friend hey only eat 4 cookies at a time, rather then get the waiter to bring you more cookies