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?
From the owners’ (shareholders’) point of view, managers are on their side to extract values from workers. Of course there are more nuances in real life, but that’s a more plausible explanation than any of the meritocracy ones.