It’s not as much the default DTH as it’s the device itself. It doesn’t report battery levels but with some models it does report a low battery condition (that’s where the custom DTH’s come in the picture). The default DTH’s in ST are designed to be as broad as possible so they don’t typically customize themselves to individual device features or settings and to focus more on the basic functionality.
Two simple examples are thermostats and locks. The default stock handlers will allow a minimum set of basic operations that work consistently across a broad range of models, but as you’ll see in the links the custom DTH’s can customize a lot of things including battery life, reliability, UI (using the Classic app for now since the new app doesn’t support custom UI’s) and also access settings/feature for individual lock models and brands. Infact through the use of custom commands it opens up new opportunities for users to use WebCoRE or CoRE to create more complex automation with minimal effort.
There are pros and cons to each approach, such as custom handlers run the cloud where some of the stock device handlers run locally for a slightly faster response. You can find more information about this on the FAQ pages.