A user whose phone has "all day charge" that has to plug their phone in at 3pm because they used it too much in the morning would be, IMO, more disappointed.

Ultimately "all day"/"36 hours" are marketing labels that are at best rough approximations of reality. Your original argument sounds like "if Apple says that the iPhone Air's 3,149 mAh lasts all day, then a 4,500 mAh battery is useless", but as any heavy phone user can attest, with high usage even a new iPhone battery will need to be charged midday, regardless of what Apple says, and an extra 50% battery capacity can be the difference between regularly needing to charge midday and not.