The village had a very limited stockpile of this item.
It wasn't because the manufacturing process was troublesome or the raw materials were hard to find, but simply because they hadn't found a reliable launch method yet. Using them in standard combat by throwing them directly would easily lead to a Pyrrhic victory, doing nearly as much damage to themselves as the enemy.
The reason Li Hu brought them along was obvious. It was a last resort. If the situation became untenable and they couldn't escape, he would use the explosives to cover their retreat, buying precious reaction time for the rest of the village.
