So it should be easy to see that when there are frequent frequency changes, route changes in the FMS, navaids to tune cleared levels to set, headings to set, speeds to set and so forth, the single pilot doing all that can get a bit overworked while his friend sits there leaning on the controls.
Indeed, and it can be frustrating when they other guy decides to 'hand fly' a departure out of a busy TMA without so much of a 'by the way I'll be..' or 'just to let you know I'll be..' while you're left wondering when he plans to stick the autos in and you're left doing all the above as he lazily follows the magenta cross with the odd flick of the trim switch and the A/T in thinking that he's hand flying it.
I'm all up for keeping up manual flights skills, raw data descents and approaches and thoroughly enjoy taking the automatics out and having to exercise some grey matter but I'd have to agree with Airbus Girl on the balance of things.