I do occasionally cook for larger groups, and you need entirely different techniques. At home, you don’t need to account for the time the water spends between 70 and 100 degrees because that’s a minute at most. When you’ve got a hundred liters of water, that suddenly becomes very relevant. If you set your timer for 10 of actual boiling, your pasta will resemble porridge.

Also, I don’t personally own cooking gear to make food for 20+ people.