Why would I need a source for something so completely obvious?
I see. So if something is subjectively obvious to anyone, the 99% claim can be slung. Now so much use of 99% claims slung around here makes great sense (not the claims themselves but their overuse to support whatever Apple says).
If iPhone battery life was a problem for the majority of users, Apple wouldn't sell record numbers quarter after quarter.
The benefits of iPhone outweigh individual user issues. THAT's why it has record sales. Those that wish is had this or that put up with the fact that it doesn't because of the rest of the benefits it does have. Record sales is a measure of the "whole". It doesn't mean it's perfection and no one should wish for any improvements based on personal wants. Else, why bother with the A8 or a better camera, etc if "record sales" says the A7 and the "as is" camera are "good enough"?
But if "record sales" is the determinant of "no problems", Android dominates the smart phone OS by far now, so, apparently, Android's "record sales" makes it the superior mobile device OS. Windows dominates as a computer OS, so, apparently, it's "record sales" makes it a superior computing OS. Etc. Let me guess, "record sales" won't apply to those arguments because "99% says iOS and OS X are the best OSs".
And like it or not, the thinness of the device, enabled by a very optimized OS and a just "normal" battery life, is a major design differentiator for Apple.
Once again, putting in a bigger battery doesn't require a thicker iPhone… especially in this shift to a wider and taller iPhone shell. If they retained the thinness of the 5s, there would be ABUNDANT space inside for more battery. If they thinned it a little, there would still be ABUNDANT space inside for more battery and those who desperately need a thinner iPhone 6 could get their want fed too.
None of the "we don't need more battery" crowd argues about the onerous thickness of the iPhone 5s. So "thinner" is a solution to what appears to be nearly no one's problem. On the other hand, there are many- even within this single thread- that want more battery life. That's a real, tangible problem or opportunity that Apple could most easily address in this taller & wider iPhone 6.
More battery has no effect on Apple's ability to deliver an "optimized OS", nor is there any loss of design differentiation either. Those kinds of suggestions- like the idea that the iPhone would have to get thicker to accommodate more battery- are just fluff or spin in an attempt to rationalize why Apple likely won't deliver on this one.
Apparently, your "99%" would rather have "thinner" over the tangible gain of longer battery life. However, I don't see that 99% griping about the thickness of the 5s, yet they apparently want a "thinner" 6 anyway.