if you have say 50-60 hours of work
How exactly do you hire another manager with that? Do you pay for the extra 20-30 hours of manager time you don't need a lot of which will end up being used because of coordination issues. For example likely they will both have to sit in some of the same meetings doubling the cost of the meeting (in terms of IT or whatever management time burned). I don't think it is necessarily a sign of incompetence it can just be a sign of reality: the money for another position or the work needed to keep another FT manager busy just isn't there.
It is never easy at the higher end of the org. It is hard to go from 1->2 network admins because you want enough work to justify both people's existence it is really hard to go from 1->2 managers. Coordination of responsibilities, cost of not having relationships with other managers will likely make the new guy less effective etc. Things aren't always simple. You can just as easily argue that anyone that is married and doesn't have two cars is practicing incompetent household management since both spouses can't independently travel easily. There are limitations to what you can afford both in business and in life in general. Not getting all you'd like isn't always a sign that your boss doesn't respect you (though it could be) or of incompetence sometimes it is just economics.
