It's an etching primer. It "eats" itself into the surface of the plastic thus promoting better adheasion of the top layers.
Never confuse mass produced lures with hand made. We had better be taking the time to do the best we can or we are doing the hobby a gross injustice. If you are having paint issues with their lure it's probably due to lack of topcoat or inferior production standards. Have you filed a complaint with the manufacturer? If we don't they will continue to make crap. Most fabricators don't care about high durability, their main concern is increased sales.