To White Hat who's wondering what's the advantage gained when the coach walks out onto the field to talk to his players, ask yourself WHY he's walking onto the field to do so. It's so he can talk to his players without the opposite sideline hearing what he's saying, OR he's trying to get closer so that he can be heard above the general din. In both cases, he's trying to get an advantage over the other coach because he's assuming the other coach is going to follow the rules. Unless you've told both coaches in advance that your crew is going to ignore the 15 yard penalty for coaches being on the field (Unsportsmanlike Conduct - rule 9-8-1i), you've created an unfair advantage yourself. Regardless of whether you've told them that or not, you've single-handedly made life more difficult for your wings due to allowing the coaches all over the field. You've taken a set rule that clearly defines what is acceptable and turned it into some gray, "Well he went out, but it wasn't far enough to flag" piece of crap. Congratulations. Yes, not every foul is flagged, but what intentionally doesn't get flagged is usually determined to have had no bearing on the play. Can you really say giving one coach a communications advantage over the other is not an advantage and thus, not have a bearing on the play? If so, then you're just lying to yourself. Finally, you are giving other crews a major headache by being one of those "we've been allowed to do this all year" problems that crews who actually enfore the rules have to deal with.
To the person who wants to make it illegal for a player to come within earshot of the coach after each play, are you SERIOUS? Just how in the heck would that be enforced? Notice I said "player" and not "quarterback". If you ban quarterbacks, then they'd just use another player to receive the instructions. In this I agree with White Hat. The referees should not (and haven't ever, in my experience) been delaying the ready for play whistle because a player was talking to the coach. Once that whistle blows, the offense has a set amount of time to get the snap off. As long as the player gets back to the huddle and the play goes off on time, there's no delay caused by the QB (or whomever) running to the side of the field every down. Personally, I think it just fatigues the QB by effectively doubling the amount of running they do in a game, but if that's the way they do things, then so be it.