If we say someone is as busy as a bee, we mean they are doing a lot! Bees do keep busy, and it is always good to see bees busily flying from flower to flower as a wonderfully efficient way of collecting and using pollen.

"Why do bees need nectar and pollen – and how do they use it?
It’s well known that bees gather these products from flowers, but why do they need them - what are the specific benefits to bees? Basically, nectar provides an important energy source (carbohydrate) – it supplies a complex range of sugars, whilst pollen gives vital protein and fats. Although all bees need pollen at some stage in their lives, not all bees gather it." - http://www.buzzaboutbees.net/why-do-bees-need-nectar-and-pollen.html

Sort of like humans, some of whom raise crops on farms to feed the rest of us.