In the Western part of Scotland, particularly in the North-West, the influence from Gaelic is very evident in the vowel sounds. At least in the Gaelic they have kept the diacritics which denote the long sounds or changes of the vowel sounds. The Grave or Acute accents give that information. If you notice, Gaelic has NO double vowel words, ie wood or look. It would come out as wòd using English spelling (the actual spelling using Gaelic sounds to generate the oo sound would be wùd).

English probably did have it but .... in the interests of "simplifying" the language, they actually made it more complicated.