I am trying to learn some thermodynamics by watching the lecture series on youtube by MIT. In the second lecture: https://www.youtube.com/watch?v=TDqx8Zv1rRo&list=PLF6C6594F42ECEE0D&index=2
From 9:00 to 9:45, the lecturer talks about why the freezing point of water as defined in the celcius temperature scale would make a bad second fixed point (the first being absolute zero), to use to interpolate between and create the kelvin scale. This is because apparently water doesnt boil at 0 degrees everywhere, it depends on the pressure being 1atm. He then goes on to say its better to use the triple point of water instead. This doesnt make sense to me since the triple point of water is only 0.01 degrees at 1atm, just as the freezing point is only 0 degrees at 1 atm. What is the benefit of using the triple point?