To have a better chance at life this seed needs to get away from its parent. That’s why nature has come up with all sorts of different ways for seeds to travel.
If animals run out of food they can can move to where there’s more. Plants can’t get up and move to find a better place to grow. But they have found ways to send their “children” to new places where they might have a better chance of surviving.
What good are prickles anyway? A prickle is attached to a seed which is catching a ride somewhere. The sharp (ouch) pointy bit attaches it to something, usually an animal.