I currently carry a huge variety of batteries. The Garmin GPS uses AA. My Zipka+ headtorch uses AAA. My Surefire U2 uses 123s. My Orb Raw uses CR2. My Photon Freedom uses watch batteries, I forget what type. My phone uses a weird manufacturer-specific battery and so does my camera.

I'd like to use standard batteries, but I'm not really willing to compromise other factors to do so. My camera, for example, is tiny and the battery takes up about half of its volume. I'm not going to EDC a bigger torch than the Orb Raw, and I don't know of another in that size that's as bright, and the type of battery is a big part of the reason for its small size. Likewise the Photon. You can't get a U2 that runs on AAs. And so on.