Perhaps unsurprisingly, in New England jam seems more popular than jelly. The FDA regulates the labels...jelly is made from fruit juice, while jam is made from fruit chunks. The only jelly I routinely see is concord grape jelly. Jams are usually apricot, raspberry, or strawberry.

Given the number of small batch jams available at various farmers markets, my guess would be that for smaller farms, making jam is more practical than jelly.