there are two options.
in option 1, you are guaranteed 90 points.
in option 2, you get 100 points with probability p and 50 with probability 1 – p.
when p is very low (very close to zero), which option will you choose?
for me, 90 is close enough to 100 so i would rather guarantee 90 so i will take option 1. some people don’t see expected value, they just see that there is a non-zero probability of 100 and go for it, and in most cases get scerwed.
i would rather make my contract than go for an overtrick and go down.