One one of the first discoveries about bees in the time of the ancient Greeks was that on any one flight, they confined themself to one particular species of plant. This is highly convenient for the plants. It ensures any pollen transported between plants will be of the correct type. You might naively think "How polite of the bees, how considerate. There is no benefit to them."
But of course abundant flowers are very important to bees, so indirectly, bees are helping themselves.
I wondered about other selfish motivations that might manifest as apparantly altruistic behaviour.
Another question tickling me is you have a chicken and egg problem with flowering plants and bees. Each is completely dependent on the other. How did this dependence get bootstrapped? I understand bees evolved from carnivorous wasps. Perhaps early flowing plants used wind or random insect movements.