I don't understand why 1) developers are promoted based on impact 2) developers are given tasks by PMs 3) PMs choose tasks based on impact. This makes no sense

I don't understand why 1) developers are promoted based on impact 2) developers are given tasks by PMs 3) PMs choose tasks based on impact. This makes no sense to me. Either get rid of the PM role and put engineers in control of choosing impactful tasks, or change the promotion criteria.