Isn't this just 'sperm is cheap, eggs are expensive'?

That's probably the ultimate cause of the behavior.

However, most insects are heavily r selected (low parental investment, lots of offspring). So the cost of eggs/parental investment relative to sperm isn't nearly as polarized as in a K selected species, e.g., humans, whales, elephants.

Though it would seem even with a slight difference in the metabolic cost of eggs vs sperm, and eons of time, the bee's "search algorithm" would be optimized/directionally selected toward favoring recall. A similar dynamic also works behind Gause's law, where two competing species can't sustain a constant population while occupying the same ecological niche, over a multi-generational timescale.

Flowers themselves just bathe everything in their version of sperm, aka pollen. Bees are so much more precise.