The 50MB limit happens to be a legacy of the Android Market – see how old that is, taking into consideration how the Android Market has since been renamed to the Play Store. In 2012, Google allowed developers to skirt the 50MB APK file limit by allowing them to throw in a couple of “expansion files” (obb files are an example of this) which could amount up to 2GB each, with executable code remaining in the APK whereas the OBB files will store some really, really large resources such as maps, audio, video, and other nitty gritty which cannot be crammed into the core app.
This new 100MB limit will allow developers can build their apps to the size that is required, instead of being inefficient by compromising on resources or to send over several MB into a bloated expansion files. The change will benefit more of the developers than the users, since it is now more convenient for developers to package their apps. [Press Release]