I've seen a few folks suggest that D&D is pursuing a more complex/inter-related path to a balance-of-imbalances this time around.
This could be one of them. The GWFer has to go STR, since there aren't two-handed finesse weapons (buh-bye, katana). The TWFer has to go finesse and thus DEX.
DEX, once you max it out, gets you w/in 1 AC of the best/heaviest/most-expensive, disadvantage-imposing heavy armor in the game. It also boosts more and more important skills than STR. It also determines a much more common saving throw. It also takes care of any ranged attacks you may feel the need to make. And it adds to initiative.
So, part of the idea here could be that TWFing is there to balance the DEX fighter, who would otherwise gain too much relative to the STR fighter due to his investment in das uberstat, eventually getting him to DEX 20. By the time he's prettymuch guaranteed that 20 DEX, the GWF is ahead on damage.
Don't know how that applies to the rogue or anyone else maxing out DEX, but it's a possibility.