Ichneumon explained that quite nicely in his reply to you:
Similarly, the "dome" on each one will be the "approximately 35% of the length of the side of the hexagon", as you decribe it, which "results in a local minimum on the area". It's just the way the surface tension forces work out, the molecules don't have to "do calculus". And neither do the bees.
I know. I answered him.