Charles Darrow, the game's American creator, wanted the tokens to be based on common household items. Presumably, British households tended to have some different objects from American ones...eg we have boots whereas they have shoes. (They're richer, see?) The iron, car and hat were common to both at one time, but - maybe because American women did more needlework - they had a thimble and we didn't. In exactly the same way, the place-names on the board were attuned to London rather than Atlantic City...their Boardwalk is our Mayfair, I believe.
The reasons for the differences, therefore, are just down to 'local' factors.