I don't know that removable batteries means anything for Joe Schmoe phone user. I mean, I've got a phone with a removable battery, and you know what, I've never bought a second battery for when the battery dies. When it goes dead, you know what I do? I plug it in and charge it! There's no absence of micro-USB chargers in the world today.
I've just not seen a use case for it.
I'm right there with you. And by the time a battery has degraded to the point where you need to replace it, you've probably already upgrade your phone twice.
If you need more power and aren't around a charger, if you can remember a second battery, why can you remember an external battery? I carry around a 6000 mAh Anker. And I prefer that over 3 extra internal batteries. It has a metal casing which makes me feel comfortable keeping it in my pocket with my keys. I can start charging it without having to turn my phone off, and it works with every phone that uses micro USB. Way better than an extra internal battery if you ask me.
Plus, every phone can be forced turned off by holding the power button now. So taking the battery out isn't a big deal.