Hey guys, is it just me or is the categorization of developer levels highly subjective? I get the feeling that every company tries to hire experienced developers as juniors because they don't know $technology.

For example my own career: I switched technologies a couple of times, while sticking to java as a programming language. For example I first worked for 3 years using JavaSE technologies, the next company I worked for hired me as junior because I didn't have JavaEE experience - while still selling me as professional level to customers (I work in consulting). The next company hired me again as junior because I didn't have SAP experience - they mostly work with SAP Java technologies which is definitely a niche. Still, they are selling all their technology consultants for exactly the same rate while paying them significantly different wages. Now when switching jobs again I feel like this whole thing is going to start all over again because I don't have Spring experience or Oracle knowledge.

tl;dr = is my observation totally off base that companies are just using these categorizations as means to keep down wages?