Senior is considered a terminal role in most companies in terms of required promotions, so you don’t have to get promoted again. Staff and principal is a diffe

Senior is considered a terminal role in most companies in terms of required promotions, so you don’t have to get promoted again. Staff and principal is a different job kinda like management is, so at/after the senior level it’s splitting into 3 - managers, staff, and senior ICs, hence numbers go down.