i'm a little slow on the uptake...but just discovered that catapults can be used to destroy those pesky difficult to reach resource piles. great to reach those piles in the water guarded by renegades.
catapults=back scratcher
tool used to get those difficult to reach "itches"....err,resource piles.

btw, not complaining, but doesn't really make sense. you send rocks to destroy a pile from far away and you put the results in your pocketbook. cheers.