Why?@daveguerrieri effectively replaced by readying - slims down game— Mike Mearls (@mikemearls) September 30, 2014
Because it makes a better game.
One of the nice things about the Modern Role-Playing Game world is that we have learned some things. Objective things that allow us to handle arguments in new ways. One of those, is that the goal of the design of the game is player enjoyment and weighing that against costs.
This means that arguments from realism can be dismissed!
No longer must we wade through pages and pages of endless debate about real world experience and what makes sense! We can simply decide what we want based on what we think is most fun.
When people talk about defending the delay action, they talk about verisimilitude and attempting to do things under strict RAW. This may be important for some people. You can see the effects of designing a game from this standpoint by playing a mid-level Pathfinder game.
The Delay action slows play down. Do you want to slow play down?
Does it sit better with people to be allowed to skip their turn and interrupt the game to take it when they want, because it makes more sense?
Let me tell you a story. Once, in a game I was in, we had a new player. There wasn't a good place that made sense for a new character to appear, so that player sat in the room, unable to play for five hours. The game ended without him getting to join the group. He never returned to another game ran by that Dungeon Master.
Verisimilitude, especially in a game where flying gnome wizards cast fireballs, can die in a fire.
The second part to this delay argument is where you might have a Dungeon Master who wants to run initiative rules as written for things like, entering a dungeon room, or maneuvering in a narrow space. This has nothing to do with the rules, which are explicitly set up for the Dungeon Master to make judgement calls to speed play along to the interesting choices and enjoyable play. If you've got a Dungeon Master who's doing that, more rules are not going to make him be less of a dick. He'll just be a jerk in more technical and new ways.
This isn't just some sentiment I'm writing up in response to (not the first) place this discussion has been had. It's a call to action for people to say, "Yeah, that isn't in this game because it slows down play." instead of getting involved in a debate over why you can't avoid taking your turn and whether it makes sense.
Of course, the design team is on record as saying, you know, you can put it back in if you want. And really, you can. The question just is, if you're houseruling ways that can complicate and slow your game down, you have to ask yourself why? What does it add? And if the answer is "It makes me feel better about the rules" or "It stops my Dungeon Master for making things difficult for us rules as written." then maybe you should examine your motivations and find out if there's better ways to address that. If the answer is "It makes the game more tactical," then perhaps playing a more tactical game is the answer to that.
Hack & Slash