True true why not have both?
Like my Z which has a 16 GB internal for all the apps and games and also an external 32 GB class 10 for all the other stuff like TB backups,movies,TWRP backups,ROMs zip files,music etc
And if you have 16 GB with expandable you don't need to move the apps to SD
Also nowadays phones are coming with 4K recording and 13 MP cam which requires a lot of memory and thus phones without external become handicapped in the situation
Case in point the new Moto X (16 GB one which is released in India ) which has a 13 MP cam and 4K recording but only a measly 16 GB of storage out of which only 11 might be available for user
In such case the phone memory can be easily filled by just recording a couple of minutes of 4K video