The first thing I do when I buy a shower head is make sure that the design has a flow restrictor ring (put in to comply with US law) that can be removed. First thing I do after I buy a shower head is remove the ring.
If they want me to use less water, then raise the price beyond the ridiculously low prices we have now, prices that clearly do not match supply with demand. It is not we consumers in Arizona that are draining Lake Powell, it is politicians who price water below any kind of reasonable supply/demand clearing price to gain some incremental love at the ballot box (also, politicians prefer command and control legislation of the shower head variety to allowing the price mechanism to work automatically). More here.