Only they know the real reasons but here I am listing what I feel

    Salman Khan has a long list of exes. Vicky kaushal doesn’t.
    Salman Khan has a bad track record. Aiswarya left him because he was abusive.
    Salman Khan was looking for a wife with the qualities of his mother, he couldn’t get that in any of his girlfriends.

    Katrina was pretty young when she was dating Salman and her career had just started so there was no scene of marriage then.
    She left Salman for Ranbir, who she wished to marry but they broke up after being in a live-in relationship.
    Salman supported her still but how can anyone marry someone who left them for a third person.
    Salman witnessed failed marriages in his family so he doesn’t wish to marry.
    Vicky kaushal proposed her for marriage soon after they started dating and exactly when she wanted to marry. They are happy together. They talk about each other in interviews and celebrate important days together.

Her upcoming movie is Merry Christmas and Tiger 3.