I've honestly never understood this attitude. You get free KP on your wonders, and a prize that would otherwise go unclaimed and wasted is collected by another player. It's not like you could get that prize. And if you'd really prefer to see that prize go to a friend or fellow instead, just explicitly message that friend or post in your fellowship chat when you're getting close to upgrading, and let them know there's easy prizes available if they want them. There's literally no downside to this.
I don't know about you guys, but I purposely hold off on upgrading my wonders if there are still some unclaimed prizes, and I will actively encourage others to add 1 KP or so, just so the prize isn't wasted. Any gift I receive is a welcome gift, regardless of whether it was given for selfish reasons.
And while it's fairly common to see one or two players from outside my fellowship putting a tiny amount of KP on one of my wonders in the hope of getting a prize, I've never experienced a 'pack of wolves' i.e. lots of players doing the same. That just sounds like lots of free KP, instead of a little bit. Frankly I'd love to encourage that sort of behaviour. *places dog biscuits next to Dragon Abbey and whistles*