Answer why should they?
So many times we feel that life would be better if only our partner changed
Most partners have difficult or odd habits
Actually so do you
This is the real world and one where your partner is quite happy with that habit
If they are not then they would have changed it.
They haven't so be clear they are fine with whatever it is you dislike
You might feel it is best for them if they changed
But why should they change?
The old cliche is also appropriate here
If you want to change the world then change yourself
Slightly modified that could be
If you want to change your partner then change yourself first
Yes it works.
Yes it is true
So if you feel your partner should change whatever habit it is that annoys you
Then you change first
Change your own habits
And if you do not want to because you are happy with yours then why should they?