I had a female CS professor who noticed (and disliked) that students were a lot more likely to use her first name while calling male professors Dr. Whatever.
A lot of men) tend to perceive women as warmer, more nurturing, more approachable than their male counterparts; their approach to them is less formal, less respectful, more chummy. There are situations where that approach is appropriate, but the tendency to use it with every professional woman you meet is a problem.
I always thought it happens because we tend to use the identifier that is the most unique. We had a CS professor (male) who had an unusual first name, everyone referred to him by using the first name. Obviously not in a formal way but when we discussed him.
Because women tend to be less numerous in CS and similar engineering professions, their name tends to be more unique than male counterparts. I know it's anecdotal but it seems to line up with my school years where depending on whether your first name or last name were often we fell back on one other other. A girl with a common first name was called by her last name, while a guy with common last name was called by his first name.
Few examples in popular culture:
Hillary,
Bernie (relatively unusual first name),
Trump,
Warren (I think no one calls you just Elizabeth, her first and last name are relatively generic so usually people use both)
In Formula 1:
Lewis,
Alonso,
Vettel,
Max (or Verstappen),
Lando.
A lot of men) tend to perceive women as warmer, more nurturing, more approachable than their male counterparts; their approach to them is less formal, less respectful, more chummy. There are situations where that approach is appropriate, but the tendency to use it with every professional woman you meet is a problem.