The company I worked for until very recently enforces quite the opposite rule - they insist on the use of the highest level of automation available at all times.
I can't help but think that the modern trend towards finger pointing when the proverbial hits the ceiling fan has accelerated this idea. To put it bluntly, the airlines who steadfastly follow manufacturer's instructions to the letter might alleviate at least some (if not all) of the legal liability brought about by an incident or accident. Try flying by hand, and if anything goes wrong, the pilot/airline has nothing to fall back on.