We have Hendrix to thank for positions 2 and 4, as he's the one who, while constantly pushing his guitars to find all tones, used these positions often. So often, Fender switched from a 3 way toggle to the 5 way. Watch any Hendrix videos and you will see him placing the toggle in those positions. Had to be tough in a live setting.
I used to think that SRV used the neck pickup often, but after having Texas Specials in my Strat, learning his music, and watching his videos, a lot of his solos are the bridge and middle pickup together. Often, I felt guilty playing this guitar because with the bridge and middle position it sounds so much like SRV. I have this Strat for sale now in favor of my two Teles. I put Tele Texas Specials in one, and the Tele version sounds a lot different than its Strat brother. I find they're bigger in the Tele.