At least in the Great Highland Bagpipes, the drones use single reeds while the chanter uses double reeds. What is the reason for this, and would the bagpipes still work if the chanter had single reeds and/or the drones had double reeds?
The drone reeds are typically of the cyclindrical shape with a little vibrating tongue. This is a much more robust mechanical construction than the oboe-like chanter-reed, which eases the handling. If I remember correctly, it also has a positive effect on life time of the reed. (I try to get this confirmed by a player and will update the answer.)
Given that the single reeds are considerably cheaper and just a single pitch (i. e. single resonating frequency) is required, it seems reasonable to restrict the investment to the essential minimum.