The reason is:
1) The way electric basses work, more energy is above the fundamental (41hz or so for open E) than is at the fundamental. It's just the nature of the string length and gauge of most basses. Search talkbass for 'waterfall plots'
I have been re-reading this thread to make sure I at least learned a few things... I missed this the above "waterfall plots" the first time.
I did a search and found a thread...oh what a thread, at one point greenboy described the OP as a sitting duck walking down a plastic hallway... well I read every post in it out of fascination of human understanding... and saw the OP as Homer Simpson getting pounded in the ring, but feeling he won because the other guy passed out from exhaustion... then along comes a good Samaritan who convinces the OP what he really must have meant was "x" and rather than leave well enough alone Diggs at the people who answered what he asked... it was an f'n site to see. HOWEVER I learned 2 things from that thread... 1) if that guy ever gets his answer he will also have a camera that can tell you what the best color is for you car, and ultimately lead to the answer of the millennium "what is the best bass for metal"
and 2) greenboys link to waterfall plots. greenboy I hope you know while your original goal posting on there (post #26 I WILL NEVER FORGET) may not have hit home with the intended target, it completely change my perception and understanding of a "note". When I apply it, it answers so many misconceptions with so many other factors. I would like to thank everyone in this thread, I really love to learn and it was full of new information to me. All I see right now are graphs from WinISD so I am going to rest my eyes and actually play the gear I have for a bit... then I might order a driver... maybe some thai food