Crabapples are often included in commercial orchards to assist in cross pollination. With smaller fruit and a generally smaller growth habit they can be included in an orchard layout utilising a minimum of space while not being mistaken for the intended crop at harvest.
Crabapples also flower on 1 year old wood which means they can be cut back reasonably hard each year and still produce plenty of flowers.
The inclusion of a couple of crabapples in domestic and small farm orchards will assist effective cross pollination while adding considerably to the aesthetics, not to mention the opportunity to make crab apple jelly or add crabapples to cider blends for extra depth and complexity.
The table comes from the NSW DPI Agnote 4-77, Crabapples as pollinators, click HERE to access the note (25/3/20)