This is not a linguistic issue, it's a matter of PC (political correctness)...

From a linguistic point of view the question is whether there is a meaningful difference between what the word means when applied to a male and when applied to a female.

We easily refer to them as doctors whether they are male or female. Some may prefer one sex over the other for purely individual reasons (and when we are talking about an individual's well being they can easily be valid reasons, on an individual level), but no one ever seems to think that it would be proper to refer to doctor vs. doctress (or doctrix). The erstwhile stewardess became the flight attendant when the occupation started getting a large number of males filling positions. As with the doctor, except for individual preferences the job done by a male is not in anyway different from that done by a female. In cases where it does make a difference (and other than, perhaps sex worker, or even actor/actress, I can't think of any just right off hand) there may be a reason to have a separate word.