In Haskell, a lot of collection libraries define two operations, such as these ones from text:
cons :: Char -> Text -> Text
snoc :: Text -> Char -> Text
(The name snoc comes from being the reverse of cons… geddit?)
So really this parameter order is so intuitive that it overrides considerations of ‘less/more important’. If someone wants to specify the second parameter first they can always write flip cons or flip snoc.