What makes you think that everyone around is concerned with efficiency? With FP as the only syntactically sound number system in a language, you basically lose a == operator, as well as an ability to check if your job was finished. Or you use ints and carry fixed points around, which is viable only in few types of languages with operator overloading, like c++. Edit: even when using FP you have to carry initial precisions around, like in:

  var n = get_n() // valid to .5g
  n = transform(n)
  ...
  <input value={n.toFixed(5)}> // 5 carried over here

You can’t even infer the precision from a FP number alone, especially if it is close to log10(53). /edit

In a proper-numbers lang, if someone needed FP numbers, they could just 0.1f. Otherwise 0.1 would mean just that, and counting by 0.1+rand(100) from 1000000 to 0 would not make you scratch your head at the end of the loop and worry whether the rest is just a FP error or an algorithmic error which must be fixed.

90% of developers who know how to use FP still hate it in non-FP tasks, because there is no 0.1nobs literal, how about that.