The 738 has a roughly six meter longer wing span than the 737 classic. As far as i kow the position of the aileron relative to the fuselage was not changed, they just added a bit more wing outboard of the previous wing span. Same for wing anti ice, the last outboard slat, which covers that added span, is not heated on the 738, they simply didn't increase the length of the bleed duct.
All probably for the reasons mentioned above.