The second an associate starts, they are technically (though rarely in reality) the managers in charge of the support staff. As they become more senior (i.e., stay with the firm longer), they are put in charge of vendors and more junior associates. However, neither the original hire nor their inevitable promotion even takes into account their ability to manage people.
Associates are recruited from law schools almost entirely based on the school and their grades. Then, if they're in the margins, they are also judged on their ability to make things up interview and how they would "fit in" to the firm's culture. Never is their ability or background of managing others asked about or taken into account.
Similarly, when associates are given their reviews, they are judged primarily on number of hours worked and, as a distant second, their abilities. From what I understand, in the first couple of years, they just expect us to bill a bunch of hours and not screw anything up. Anything above that is neither expected nor recognized. Again, these reviews have nothing to do with our ability to lead.
The result is that as associates become more senior, they are given increasingly more management responsibilities without any ideas about how to manage. Sure, there are some people who are naturally good managers, but the vast majority don't have a clue. Rather than learn or seek help, they do what they've seen their superiors do their entire careers -- make unreasonable demands, fail to recognize hard work, and generally continue the process of making Biglaw one of the worst places for a practicing attorney to work.
The few who become partners, are even worse. Since they are elevated to partnership based on how much of their soul time they commit to the firm and their ability to bring in clients. A few are made partner for their skills as attorneys. But none are promoted for their ability to manage. So after years of mismanaging those who work under them, they are reworded by being made partner. Why would they ever change?
Besides making our lives miserable, this mismanagement wastes an enormous amount of time and resources, which is ultimately billed to the client. How clients -- who's General Counsels are often from Biglaw -- put up with such waste while simultaneously facing mounting pressure to cut costs, is beyond me.