@skinnylatte it is what you are used to. If I define a new scale where water freezes at 0 and boils at 1 your argument says that is good enough as well. Or I can make water boil at 1000000. Or maybe I want to make normal body temperature 100? In my garage I care about when the temperatures that O1 tool steel hardens and tempers at, so maybe 0 and 100 should be based on those?