How many computer games actually do that? If you want actual roleplay, try a MMORPG, or even better, tabletop.
Computer rpg's are perhaps more *precisely* defined as "interactive story games with a character building mechanic" and you can "roleplay" insofar as the interaction of the game and the story, but yes, asking if these games allow you to RP is a bit like asking why real time strategy games are about tactics, not strategy, the naming nomenclature shouldn't be taken too literally, and doing so is merely a good way to nit[pick the games for what they are not good at rather than enjoying them for what they are good at.