I have seen numerous manga/anime, where we actually never get to know a character's firstname.
Especially married women, and even men.
The husband calls his wife "omae", because to call her by her first name + chan or san, feels like he's addressing a friend. And after a few years of marriage, they are something more than friends. The wife calls her husband with "anata" for the same reason. They are close, but are not "friends". They are more than that.
Then they have kids.
The kids ask "where is otousan?" and the mother answers "otousan is asleep", or something. Then "Otousan" becomes the preferred way to call him in the house. Same thing for "okaasan".
In the presence of guests, the husband may just use her firstname, without san or chan, or just "oiii" to call her, because calling her "omae" can be confusing. Then he becomes accustomed to use "oi" and now the name of wife is omitted and "oi" becomes the pronoun for calling his wife. Often wives complain "I am not an oi".
It's just the way Japanese works. It's uncalled for to criticize it, I think though.
I think the fact that the mother feels strange when being called "Chitose" is mainly because it take her back to her youth and implies a level of proximity with the girl that she didn't feel in a while.