I've said it before--removable batteries in mobile devices are a must. The very slight thinness and sleekness benefit provided by a sealed device is so not worth it.
The latest evidence in my personal life--Beth's Galaxy S3 has a bad port (not sure why). No problem, we have a couple of options. One is wireless charging. Just add a $15 Qi adapter--which I actually already did, just for convenience. It fits snugly with the existing, backplate.
Option 2--buy some extra batteries. Dirt cheap--OEM-quality batteries are $10 on Amazon. I got an external charger for all of $3--shipping included (it also has a USB port, nice bonus). So convenient.
If I were a handset manufacturer (are you listening, HTC?), I would suck up the extra $5 bill-of-material cost and bundle the battery charger and a spare battery with every phone, Then I would advertise "double the battery life".
One of the subtle reasons spare batteries are so useful is the safety blanket factor. They are so small, you don't even notice them in a purse, pocket, backpack or even bike saddlebag. So instead of lugging a heavy external charger, whenever you are concerned about running out of juice, you slip a spare battery in your pocket. 4 times out of 5, you may not even use it, but it is there that one time you need it.