I found this nugget in a review of a Voodo Strat on Harmony Central.

The reverse slanted lead pickup gives this position some much needed beef. What a lot of people don't realize is that in 1954, when the Strat was introduced, amplifiers did not have a lot of high frequency response. Thus, Fender slanted the pickup so that the higher strings would be even more trebly. Nowadays, this is no longer necessary. Giving the lead pickup a reverse slant makes the guitar sound gnarlier, more solid, especially with a lot of distortion.