It would have made much more sense to replace the tapes with some kind cut scene you can trigger on mother base. You come back from a mission and you could have Ocelot, Miller, and other characters all have they own private quarters. Even Snake could of had one. You go in there, look at all the cool character details of they living area, select a conversation, and the game cuts to a cinema. Could of even just been a slide show using that lead artist they've always had for MGS, I like his style.
But instead, we got what we got for all the reasons that probably are.
I think kojima did that bc ppl complained about cut scenes being too long in previous games (5-8 hrs in total for some not including game play)
Then u can listen while u play. I got used to it n didnt mind it. Theres a lot of interesting info in those tapes that adds to the story we've all complained the game supposedly lacks. It really just lacks visuals to the story we hear in the tapes is all.