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?
Impact and risk.
Farther up the chain your decisions have broader impact, good or bad. Those kinds decisions have more value than decisions that have a much narrower range of effect.
As what my industry calls an SME(subject matter expert), at most my decisions effect one or two systems at a time, while a leadership decision impacts 10 or 100 (or more) people’s focus/direction. This includes the risks - so their decisions have a much broader scope.