On Saturday, April 8, 2017 at 6:59:17 PM UTC-6, Bruce Hoult wrote:
On Sunday, April 9, 2017 at 3:36:46 AM UTC+3, wrote:
I'll jump in as one of the organizers for the Nephi events every year:

We have pushed hard to maximize the 65 spots allowed by insurance. If insurance allowed us to have 70 spots, at Nephi we would probably have 70 spots

What makes "insurance" decide that 65 is the right number?

The 65 maximum is stated explicitly in the rules. As for the foundation for that maximum, I can't say how it evolved.