Some plants use sticky pollen that insects carry from the male flowers to the female flowers. Sweet nectar offers the incentive for the insects. This seems perfectly elegant, since nothing is wasted, not even really for the plants.
Other plants use light, wind-borne pollen. These plants scatter giant clouds of the stuff, just on the tiny chance that pollen lands in the exact right spot to fertilize the flower. It works, since the plants and trees that use this continue to use this. Seems wasteful, though, as these trees and grasses spew out an awful lot of pollen for the results.
Of course it’s the blowing clouds of pollen that trouble people with allergies this time of year. The immune system sees the foreign as an invader to be attacked like bacteria or viruses. I wish I could teach my body that pollen, while not part of me, is harmless. Actually, I wish I could teach a lot of people that foreign, while not part of us, is usually harmless.