Peter's principle and whatnot, but I think there is something deeper. The manager positions are designed, by definition of the word, to manage, and the top goal is to extract values from workers. Managers (and product managers in tech companies) are encouraged to create a `healthy` tension with line workers (software engineers included) in work estimation and commitments. This is supposed to make the work challenging enough, but not so demanding that burn out the workers. The best managers can do that by providing the intellectual challenges and motivational goals. Most resort to processes and plain OKRs though (reflected in the worst ever software tool, JIRA. Also any line manager who's got any clue, meaning who can provide technical/business directions, would be quickly promoted to directors (where they are supposed to direct :-).

Protip for frontline managers: The percentage of time you spend on JIRA is negatively correlated to the chance of being promoted to the director level.