Most of the issues in embedded programming involve asking "what's going on in there?" In small embedded work, you usually can't print, you may not have a display, everything is time dependent, and you're directly connected to hardware. Debugging may involve an oscilloscope and a logic analyzer. Using a debugger means halting the machine, and isn't helpful if the problem is timing dependent.

For some jobs, you need a simulator that lets you debug in a more friendly environment. There's one for an entire Android phone, for example.