See, that's what you would think, but it isn't going that direction. Apparently the cost of remaking a game is pretty near the cost of developing an entirely new one. Even though the shelll of the game is there as far as story/plot/mechanics, developers have to start coding it from scratch.... Or at least that is the claim.
So right now, the choice is to either make a new game or remake and old one, and I guess many companies just aren't willing to put that kind of cash into something old? I don't think they yet realize the interest us millennials would have in the remakes, since everything is always pushing for new, New, NEW!!
Perhaps one day they will figure it out.