I guess they feel the IFE and Cabin lights are most likely to cause smoke or flames wheras there haven't been any problems caused by the reading lights?
IFE and Cabin lighting are two areas that many operators retrofit systems and these are more likely to cause problems than the standard fit reading light system. If you read the link I provided above, not everyone agrees with the intent of the SB and some operators have applied to dodge it.
That's my take on it anyway.