We have to remember that Spock's betrothal to T'pring was an arranged
one, an agreement between their parents. In that situation Spock reveals he really doesn't have genuine feeling for T'pring other than a sense of responsibility. When his fever had passed and T'pring's character revealed it's easy to see how he'd have no further interest in her.
Interesting that Sarek managed to break tradition to marry Amanda, a human woman he clearly loved. And yet Sarek is pissed for decades because his son didn't follow his wishes and adhere to expectations. I'm quite sure Sarek raised a few eyebrows when he chose to marry an Earth woman.