Sometimes chickens just don't like a particular mix. Give them a few days, but if they don't change their mind, then try another brand.
Try to use the feed with within a few months of the production date (generally on the label attached to the bag). Also, make sure that it didn't get wet and...
Money is certainly a factor. We can't (and shouldn't try) competing with factory farm eggs on price. We'll never be that efficient... or that cruel.
People make their own decisions- many will want to go as cheap as possible, some will have other priorities like non-GMO/soy/whatever, some will...
My girls have been getting 18% feed from the beginning and are quite happy and healthy. You are getting BS. 16% is minimum, not optimal protein for health. Just like how the human recommended daily iodine or vitamin D intake are orders of magnitude too low for optimal health.