C.E. Evans wrote:
But the set up (which is my point) is the same way, including having different insignia--and in some department, different duty uniforms as well--for those with the rank of lieutenant and up. They're all referred to as police officers regardless if they are a corporal or a colonel.
But the set up is not the same.
Actually, it is. It doesn't have to be literally
termed as commissioned and noncommissioned, but there is indeed a distinction between those who do "grunt work" and those with administrative duties. And as with police departments, it could be easily be a case that all Starfleet personnel could be referred to commonly as officers regardless of their actual rank or duties.