Is it that important? In a relationship, values and ideals tend to align over time. I mean those that weren’t since the begining.
But if they don’t, and it is something that important to you, that is a deal breaker.
On the other hand, people always have good reason for their behaviour. Not changing something even for a loved one, is a give away that they probably have been forced to act the opposite way in the past. Which means, they are asserting their freedom.
Since it is a freedom issue, pushing it isn’t going to help. You can remind them about this, but since it isn’t something they don’t want to face or release fully but need to feel in control of, they may take a while or not try to fix it at all.
But really, pushing it never works. Having them talk and express how they feel about it while showing understanding (instead of just disagreement and expecting them to change) can be transformative enough.
This is a reminder to myself, don’t take anything personal.