Some managers fall into the trap of stepping in and bailing out their lower performing employees. If certain staff members are not doing their jobs satisfactorily, a knee-jerk reaction is to jump in and do it yourself.
This isn’t a good idea. Not only do people not want to be micromanaged, snatching work from them (because you’ll meet the deadline or think you can do it better) is demoralizing. Over time, they will think, “Why bother? The work will never be good enough for my boss and she’ll just do it anyway.”