The challenge was a surprise to Spock, it wasn't anticipated. T'Pring and Stonn knew it was coming, perhaps T'Pau too, but not Spock. This leads me to think that the challange is unusual occurance in the typical Pon Farr cerimony. So if Spock had tried simply running, he would have dropped dead at some point.
It seems pretty obvious that the challenge is rare (after all, I'm sure the Vulcans don't want to slowly exterminate their own species by killing off perfectly strong and healthy young (presumably also virile) males in marital challenges.
Plus it doesn't seem like T'Pol had a challenge at her wedding, which was a far more private family ceremony. Some of the challenge may have had to do with the pomp and circumstance of being in a rather public ceremony.
One bit o' wackiness, though – neither of Spock's parents show up, and they aren't even mentioned. And it does not appear that T'Pring's folks are there, either. Now, hers might be dead, but his aren't. A marriage of your child is a major life event, and Spock was not estranged from his parents. A simple, "Sarek and Amanda couldn't be here." would have fixed that.