Because while it is simple, the power is out while I do it. When it is just a single circuit no problem, but if I'm missing one part that means several more hours while I track it down (home depot might or might not have it). A real electrician will have the parts on the van, or at least know where to get the missing one. Not to mention there is probably power to the box, while I can work on live circuits I prefer not to. (or if there is no power, that means there is no power for days because I work on weekends, then the inspector comes on Monday, and only after that does the power company reconnect).

There are some jobs that I can do, but I hire someone else to do anyway.