I don't think you need to reach for sexism as an explanation there. Name changes are sufficiently rare that building the flows to support it will usually only become an issue in mature production software where accurate names are extremely important, and where preserving long term records is equally important. That's not most systems. And that's before you get into cases where names are primary keys like usernames.
The business case for supporting such changes can be pretty weak relative to other features.
In recent decades, about 80 percent of brides choose to change their names after the wedding, both professionally and legally. [1] Most people marry at least once. [2] Women are half the population.
That being said, I do agree that in many systems, supporting name changes is not an immediate priority.
The business case for supporting such changes can be pretty weak relative to other features.