"It won't streamline the system, but it will make the game flow faster at the table". That's a non sequitor. If you've got bloat in the system, you've got bloat at the table.
It's the whole idea that rolling dice is more fun for more people than crunching numbers. It's significant in that it involves bodily action, the physical movement of the player, not just the mental challenge of adding +1's. It shakes you out of your "sit there and tell me what your character does" kind of baseline for most of the game. It's not inherently better, but it's easier to remember by it's very nature of being an active process that demands instant player input rather than the passive process of adding bonuses that just demands a player have the correct output.
It's not BETTER, but the difference enables more activity from the player, and if you're looking for more action in the game, this adds it. It does take away an aspect of cerebral play, but with all the complaints about D&D's complexity and too many buffs and the challenge of adding up all the scores right, it seems that D&D, in this respect, may be a bit *too* cerebral for a lot of players and DM's. Heck, even OotS did a strip about all the little +1's and +2's that some players just forget. This has been a problem in D&D, and reducing the number of minor bonuses is the solution.
This reduces the number of minor bonuses and replaces it with active player input. Instead of just remembering 10 +2's, you remember that you get to roll your dice again (for instance) if you don't like the result. You get to steer the ship during play, not just in between sessions when choosing the right skill or feat.
It's a bit of simple human programing, in the end. It's why people still remember the Capcom Code but forget Pythagoras's theorem. It's why languages are taught aloud, why songs you can sing along to are easier to remember (even if they're not particularly good songs): When an action requires you do actively do something, it's easier to stick in your head.
It seems that a number folks in this thread have already jumped headlong into the "adding numbers slows the game down" bandwagon without giving the matter much thought. Actually, it's more like "remembering all the numbers to add slows the game down". Which is the whole point I've been trying to make here. To reiterate: if you still have tons of stuff factoring into your checks, you still have tons of stuff to remember to factor in.
I think with the amount of complaints about high-level complexity, too many buffs, and the common error of "Whoops, there's a +2 synergy bonus here!", many players have found that adding numbers *does* slow the game down for them, and so for them, it's not quite as fun.
And while these other rules certainly have potential to become as bloated (for instance, allowing you to re-roll an action more than once), each individual rule itself is easier to "stick" because of how people learn by doing, not just by thinking.
