As far as I know ArcGIS needs Android native library support, so it adds 'libruntimecore_java.so' to 'libs/armeabi/' and 'libs/armeabi-v7a', however each file is 10MB... so the application we are developing weights 20MB+ due to ArcGIS.
Currently we ship with all native code in a single *.so file. You don't necessarily have to include both the /armeabi and /armeabi-v7a folders with both lib files. Depends on what devices you are deploying to and supporting. armeabi will work on all devices but will be a lot slower and won't take advantage of newer devices CPU capabilities. The package manager will only install the libraries from one of the libs/<abi>/ directory, depending on your device. So you can reduce the size by removing one of the libs/<abi>/ directories.