Sadly, I've had about the same amount of time in retail, and while there are indeed plenty of polite folks who've I've bent backwards over to help, I know for certain there's a far larger amount of folks who raised a stink and threw a fit and gotten a larger reward from it than being decent would give.
Wherever being nice rewards you, being a psychopathic piece of shit will likely reward you even more.

I've had a boss authorize me to give up to 25% (staff) discounts at
a fucking dollar store if any customer starts to cause a scene. Teachers got 10%.
And of course, there are good people despite the incentives not to be, bless them