It's not just programmers. Plenty of genealogists, do things like automatically give a wife their husband's (male!) patronym. Even though they see it doesn't work that way in the sources, they seem to feel that it "should" work that way.
Nom d'usage technically has no legal value, it's just a last name you might want to be addressed as, normally that of your husband but it can be a pen name and whatever. It's optional, and technically only at the request of the relevant person. Men can have nom d'usage too (égalité, after all).
Still, immigration offices, banks, insurances... they often slap the husband's last name if that field is left empty, just because. Why would you want something else, right? She probably forgot!
We started crossing those fields to make it clear she doesn't want a nom d'usage.
We actually couldn't open a joint bank account with both names separated. They'd accept the papers signed in the official names, but the names on the cards and other communication needed to be unified for their system to accept it. They'd accept to reemit card with the correct names only as an exception by abusing the card renewal system apparently
Most people never need to think about the details of how names might work in a different culture across the world, let alone work that into any kind of a rule-based mechanism or a rigid information model. If some random person working at a construction site in Europe or the US has no idea that first names and last names aren't a universal thing, that has exactly zero direct effect on anything. In most cases that's probably even true of lawyers or other high-level white collar work.
I'm actually inclined to believe lots of programmers know more about e.g. time [1] than a non-programmer Joe Random does on average, exactly because software developers may actually end up coming across at least some of those issues.
[1] e.g. https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b...