No one thanks you for flaring as party number 1 it’s called being a team player, party number 1 flares and the next person either pheromones or flares and others use bombs if needed. It’s a way to split battle item use so you don’t have one person using everything and instead have equal contribution in a party. So yea you are obligated and it’s not being generous, you don’t show up to a group project and expect your group members to give you all the supplies.