I've read in more than a few books, that bees prefer natural nectar
to ANY thing else. I'm just guessing here but given your location, I
think your bees don't need to rob or take syrup cause they have
a much prefered source or sources within foraging distance.
I seem to recall you posting about your bees bringing in lots of
pollen, if that's so, would they not be getting nectar as well? Maybe
your bees ignore honey in frames and offered sugar water cause
they have something better goin' on
I was watching my hive for a while today and about every fourth or
fifth bee coming in had huge baskets of bright yellow pollen,
they were bringing in some orange colored too, just not as much.
I'm assuming the other girls coming back were bringing in nectar...