Never as in literally never since September, or just not very often?
And if the teacher doesn't hear them read, does someone else in school (like a TA?)
And are you sure they don't hear them read. I never remember to write in a child's reading diary when I hear them read, but we have logs in school.
I'm a TA. When I worked in KS1 each child was heard once a week. The teacher and I would read with half the class each per week and then swap the following week, so they'd be heard by the teacher once a fortnight. It was much harder, however, for her to find time to read than me so quite often I would do two thirds of the class and she'd do the other third. Still, the teacher heard them read twice a half term.
Now I'm in KS2, the expectation is that the 5 or 6 children who are struggling the most with reading are heard twice a week, the ones who are not reading at the expected level for their year group are heard once a week, and those who are working at the expected level for the year group are heard one a fortnight. I heard 90% of the readers each week because the teacher is... teaching. Whenever she does have time to read, I look at the children available and then pick the one she heard read longest ago. It's possible there are some children (particularly those we read with once a fortnight) that the teacher has never read with 1:1 because they're not around when she has time to read, so I end up reading with them at other times when she's teaching the rest of the class.
TL:DR - the teacher should be hearing your child read (at least once a term, I'd say - depending on age). But if a TA is (providing they've had training on reading) then in practice that's just as good. The teacher I work with is constantly asking me which book band comes next, or what book bands particular children are on, because I deal with it more on a day to day basis.