Why do we say Salt to taste and don't say salt according to taste or salt for taste?
It is a shortcut for
salt [according] to [your] taste
Transversal post : http://www.thekitchn.com/food-science-salting-to-taste-49868
It's obviously a deleted form.
The only evidence that I can think of that the word 'Add' (salt being the noun) has not been dropped from an original is that the parallel
'Dilute to taste'
is also used. However, there is an argument for the contrary:
'Spices (to taste)'
is used, and 'Add' must have been deleted here.