Inertia

"I'm astounded by the inertia of bad ideas." - from 'The Know-It-All'

In this case, the author was referring to how farenheight was anchored.

0 - the temperature at which an equal mixture of salt and water freezes
30 - the (inaccurate) temperature at which water freezes
96 - the (inaccurate) temperature of human beings

The problem, of course, it that it's usually easier to stick with how things have been, than to gain the momentum to change anything