I agree completey! The needs of mothing and CPs are contradictory
I have 10 large water butts which were all full until a few weeks ago. Unfortunately, we are in the middle of a bathroom extension which means I've had to drain the 5 on the house - all were getting full of mortar and cement powder and I was worried about the effects on pH. This means not only have I lost 1/2 my water stores, but I also can't refil them until the builders are finished. 3 of the other 5 butts are full, but collect more slowly as they are attached to the greenhouse.
On the other hand, rain does interfere with the 'normal' gardening so you can't win.