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?
It comes down to jealousy. A manager can’t possibly make less than their direct reports is a common thought process, especially when both positions are salaried. Some companies are willing to buck the trend and pay at least first or maybe second level managers less than some of their reports at times.
It’s actually somewhat common for roles with commission or tips to make more than management. This also happens with roles that get paid overtime.