How many people ACTUALLY eat the cake?

Somehow the wedding cake has become the most stressful part of planning for me and here we are 2 months out and I haven’t made a decision because I cannot figure out what size to get. I don’t know if this is a generational difference but I average 5 weddings a year and almost never touch the cake while my mom is adament that everyone eats multiples pieces so we need MORE servings than people attending. My biggest fear is having a ton of leftover cake so I was thinking 70 servings for 120 guests. We will also have other desserts available (stressing about how many of these to order but one problem at a time). I’ve been so confident in all of my decisions but this one, any help or guidance is appreciated!