That, in a nutshell, is why we have regulations on who can represent themselves to the public as an "Engineer". People can call themselves anything they like, but when they want to advertise to the public that they are an "Engineer", the registration requirement ensures they meet a set of minimum requirements to do so. There are many who would like to call themselves "Engineers" without having to earn at minimum a Bachelor of Science in Engineering from an accredited 4-year degree program. Many would like to use "Engineer" or "Engineering" in the slick marketing they do without having spent an apprenticeship gaining skill, knowledge and experience working under a licensed engineer before sitting for the principals and practices exam. The public doesn't know the difference -- and that is the reason for the registration requirement.