Pretty much every company I’ve been in or know of values a vertical trajectory instead of a horizontal one for its employees i.e becoming a manager nearly always means a faster salary progression than becoming an expert in one or multiple fields.
Why is expertise valued less?
The higher you get up in a company, the more it will be about running the company instead of what the company does in detail. While we all have our gripes with middle and upper management, such a structure will come naturally with a growing company. Really small companies often have owners and management, who are themselves experts in the field. For bigger companies that is not really achievable and not even wanted, since management has a lot to manage.
When you become an expert and want to climb the latter, then some management will automatically come to you. You will be asked to lead colleagues more junior than you. You will be asked to manage strategy for your field of expertise. You will be asked to assess the effort needed to handle projects and the risk assiciated with them. This already means quite some management work. The reward is, that (if you do a good job) those under you will be able to do a better job and that they have time to themselves become experts by doing the technical work.
Thats my current situation. In my IT job I have to do all of the above to guide the project into success while giving some of the technical work to those more junior. For some this is good. Though I personally probably won’t go much further into management positions, because I don’t like that work enough.