If you've ever played an "E" chord on your Collings, then there ya go. Relates.

The real answer:

Because "E" is the peoples key.

My last word on the subject (Doc's right...what does Bill Collings care about perfect fourths!). Perfect fourths were considered "consonant" in common practice harmony only under certain circumstance. As an abstract interval it was given the name "perfect" because of it small ratio. But this is old, old theory and has little to do with practice (I'm a music theorist and will be the first to admit that theory and practice often make rotten bedfellows!). When writing two-part counterpoint, perfect fourths were avoided or handled very carefully. In counterpoint or part-writing of more than three voices, perfect fourths were more in use, but only (i.e., only = most often) if they were not formed between outer voices. As music "evolved," the need to hear the perfect fourth resolve to a major/minor third influenced the way this interval was regarded.

Oops, gotta go to class. Let's move on...