It is a good idea, because with PHB and DMG in one book, you don´t have those pesky players only buing PHB...
no, seriously... the PHB/DMG split is one thing I really would remorse... A Player should have all necessary things to play the game, the DM should get the material to run it. There are things, a player really should not know... but that is very old school feeling of mine... I hated it back then, but we were not allowed to even look into the DMG or the MM. It really made the experience better!