Well, historically, because IE7 didn't support it last time this was brought up made
pre-wrap an immediate no-go, as it was a supported browser at the time.
But...even now, it doesn't really address the long un-broken line of code that a scrollable area does. Pretty much, a lot of Java questions would have:
....that doesn't wrap correctly, but scroll bars handle it. (Test it yourself!)
Also, auto-wrapped code can be much uglier, especially when parameters and such can be manually spaced to fit the visible space in a much cleaner and more readable way.