Pollen = Protein
Nectar/Honey = Carbohydrates
Just like most other living animals they need both to survive.
Honeycomb holding Pollen -- the multicolored cells are pollen, actually something called "bee bread" if you need a keyword to read more about it. https://s-media-cache-ak0.pinimg.com/564x/c2/65/36/c26536d91...
This image shows a comb with pollen in the bottom left, uncapped honey/nectar in the central area. This uncapped nectar has too much water in it still and will ferment, and capped honey in the top right section. This capped area is true honey that has been dehydrated enough to not ferment and spoil. http://thumbs.dreamstime.com/z/honeycomb-fresh-honey-pollen-...
It's the original Sharing Economy.
I keep bees and they absolutely do store pollen in the hive to use as food (as well as nectar to turn into honey).
"First bees have four main items on the collection list: nectar, pollen, saps / waxes, and water"
[0] - https://www.quora.com/Can-honey-bees-collect-nectar-at-the-s...