Re: Hate Children/non-committal Sims have try for baby fail all the time
Sorry, I misunderstood what you were talking about. I thought it was that you weren't getting sims with those traits pregnant, not that they couldn't even try.
Anyway, I went and tested this and you're right. If a sim has either trait and is asked to Try for Baby, it won't happen. If both sims have either trait, you can't get them to Try for Baby at all. I tried with several variations of trait combinations and they did the embarrassed animation every time and wouldn't woohoo. Regular woohoo was fine, but Try for Baby just wouldn't happen.
I did find that it depends on who does the asking so sims with those traits can Try for Baby. If another sim without either trait asks a sim that has either one of them, Try for Baby won't happen. But if a sim that has either or both traits asks another sim that has neither, it does work and you can Try for Baby.
To me, it does make sense though. One hates children which implies they don't want any children and the other is non committal and doesn't want children as that is a major commitment. So the change does reflect real life a bit more now and those traits have more impact and meaning now. But if either does decide they want a child it is still possible unless both sims in a relationship have one of those two traits. Then you end up with a childless couple unless they adopt. I did check that and a sim with either of those traits can adopt.
Hope this helps.