Why are honey bees not useful for pollination in greenhouses and what bees are?

Why are honey bees not useful for pollination in greenhouses, and what bees are?

Honey bees would come out of their hive and fly up and away from the crops in the greenhouses to forage over an area of at least several square miles. Bumble bees naturally fly much lower and “bumble” around inside the greenhouse because they naturally forage a few hundred feet at most from the nest established by each queen.

The photo is of a shipment of bumble bee queens in their nests for shipment to greenhouse growers from www.greenhousegrowers.com .