I don't know if they still do, but I believe United Airlines used to do just that. My understanding was that when you selected autoland on the 767/757 fleet, the flight director would disappear.
When I was flying these in UK the CAA stipulated this setting. I then moved to a european airline, different CAA, and the FD remained. So it was not a type issue.
I am leaning strongly towards the idea that to improve monitoring of 'what the a/c is really doing' the FD's should be absent when A/P is in command.
However, and sad to hear, there are airlines who forbid switching off the FD when either manual or automatic flight. That comment might be more relevant on the 'too much auto-dependancy' topic when considering manual flight, but does has some relevance during automatic flight.