A passionate connoisseur of fresh powder snow can tell you with authority that on that perfect Alpine day, it refuses to stick to anything, and leaves any smooth surface readily .. however we are pilots, there are policies in place to encourage good practice and avoid unnecessary loss of life, and that is our job.
Clean wing policy is what it says .. and if you think you know better on any given day? fine, take it for a circuit with no pax first and see how much your company thanks you. Test flying with pax is not professional whatever the departure from SOP .. QED