There is obviously no 'better' way to have the rotor rotate.
Legend has it that the French got one part of a Flettner machine as war reparations and used that for their engineering, and since it turned clockwise when viewed from above, they stuck with it. Given the relative maturity of the French rotary wing engineering prior to the second war (they had the first hovering helicopter in 1909) that's a bit far fetched.