It closes doors because there is no good way for them to proceed. We essentially have no good answers for how to get involved with a woman both professionally and romantically in some ethical, above board fashion.
So men who are attracted to me are damned if they do, damned if they don't.
And I can't trust their motives. Are they helping me because they think I'm smart and talented and a good fit for a project? Or are they helping me hoping it leads to sex?
In practice, they usually don't make any effort to help me professionally anyway. Once they decide I'm attractive, in their minds the relationship is strictly personal and not professional. Period.
My experience has been men consistently decide early whether this is a platonic/professional relationship or a potential romantic interest. If I'm a potential romantic interest, I'm basically dead to them professionally.
They also tend to only think about how this impacts their career, not mine.
When I had a corporate job, one senior programmer in the IT department asked me for a date. In five years working there, he was the only person I met who knew what GIS was without me having to explain it. (I have a certificate in GIS.)
He interpreted that as "We have things in common and she's hot." He did not wonder if I might be an asset to the IT department. He did not wonder if I wanted a job in the IT department.
I did, in fact, want a job in the IT department. Being asked out by him did nothing to hurt his career. He was doing nothing wrong.
I'm sure he stopped to consider that. I'm sure he stopped to check that asking me out was not a fire-able offense.
He likely did not wonder how it impacted my career at the company. It made it vastly less likely I would ever get a job in his department.
This was true whether I said "yes" or "no." Simply being asked for a date, regardless of how that went personally, made it vastly less likely I would ever get into the IT department.
I left the company a few weeks later. I likely would have left anyway and had been planning to do so for some time, but him asking me for a date was something of a final nail in the coffin, killing all hope that I had a shot at a real future at the company.
I didn't. That simply was a non starter.
So it made it easier to pull the trigger on plans to leave.