Given that the masks are designed to protect others, I tend to wear mine until the door is closed not primarily for public perception (I'm sure most who see us unmasked while boarding assume they interfere with our duties anyway), but to protect the gate agent, baggage handlers, flight attendants, fuelers, or any number of personnel who may need to come up to say or check on something.

Until this thing is over it feels selfish talking to strangers in confined space/close proximity without one. Once the door closes, risk of them interfering with duties outweighs reward of their protection against the virus. Additionally, significant changes made in the flight deck environment after brake release need to be studied and regulated as they relate to the operation, and face masks haven't been. Although I do not think they make it that much more difficult to hear through lol.

That being said, I'd be curious about coronavirus prevalence among airline/airport employees. Delta CEO said maybe a few weeks ago in an interview that positive cases in their flight attendant group were below any and all national averages, which is encouraging.