/summon Villager Farmer NBT tag canPickUpLoot will default to 0

Typing in the command

/summon Villager ~ ~ ~ {Profession:0,Career:1,CareerLevel:1}

will summon a farmer villager. The villager will be able to harvest wheat, but will not pick up wheat or seeds. Looking in the NBT data the villager will default to canPickUpLoot:0.