Battery life

I know that this is one of the biggest issues with phones today. I often listen to people begging for removable batteries, even claiming that a unibody chassis is a deal breaker, despite having all kinds of goodness from specs to aesthetics on the device. (I've already read this many times for the HTC One)
But I can understand that. If there's a problem with your phone, you just change the battery (with an even bigger one if you want) and you're good to go.

But things get weird (to me) when I see people saying "I want a full 2 days with one charge".

Why? Why in the blue hell? Don't you go back home at night? Can't you just plug it through your sleep time or at least once during the day? Seriously, I don't want to point the finger at anybody, I'm just curious. I really don't get it.

I have an iPhone 5 and, albeit being very well optimized thanks to the software, battery life definitely sucks. If I turn 3G on it's easy to see it dropping from 100% to 80% without even using it at all (maybe 5-10 minutes) in a few hours. I really need to be careful (that's annoying, indeed), and I can't even imagine what is going to happen when I'll switch to LTE. That's why I'm always with my 2G Edge data on (that allows me to recieve push notifcations and emails, other than iMessages), and if I ever need to go into the browser (or just something "heavier") I switch on the 3G and turn it off once I'm done. And that's it.
But at the end of the day I always manage to get it until, say, 10PM. And in the meantime I have several occasions to put it in charge, occasions I take advantage of. I know, it might be annoying, but if you're working on a computer or you're more generically in a closed space, you're probably next to a wall socket. And if buying a second Lighting cable is really pesky, micro USB cables are everywhere. I have like 5 of them at home, and I don't even know why or where they are coming from. And that makes me think (and wonder why the iPhone 5 was my first smartphone, but that's a different ballgame).
I'd rather bring a stupid cable with me and plug the phone in if I need it (and have the chance) than not buying the device I love because of that problem, especially given that despite the Note II and the Motorola's MAXXs every phone is in a kind of average battery life.

This is just an idea (what I do everyday) and I understand how annoying it is, I understand that not everyone can actually do it, and I eventually understand the general demand for phones that don't give these kinds of problems in 2013, to which i tag along.
But what I want is to go back to the original observation; 2 days? Really? Isn't one (a true, full one) enough?
I want to ask you guys: what do you demand from a phone battery then? What do you think?

Please remind that I don't want to start a polemic discussion, just bring a normal debate up. Sorry for the bad english.
Thanks :D