"Sorry, just saw the "busy schedules" response. So all of the time options, including 7 days, isn't enough time for you to enter orders? Therefore you eschew discussion?"
I really hate to pull rank, but until you've played some games with high-level competition in them, you're not going to understand how big a time commitment FP really is. If you're not capable of checking in roughly every six hours or so outside of sleeping, and writing reasonably detailed messages all the while, it's impossible to stay abreast of the diplomacy on the board and to manipulate it to your advantage in these kinds of games. When I'm fully invested in an FP game, I'm very likely committing 10-15 hours a week to that game exclusively. In a gunboat game? Maybe 10-15 minutes a day, depending on whether people ready up or not.
There's a separate motive that's particular to me that I can share too, although I expect most people don't have to deal with it as much. As contradictory as it sounds on the face of it, after my talk earlier of how much time it takes to play FP, the game is too long. Press is fast-paced and it seems like there's never enough time, but the actual duration of the game is deceptive. If you make it to the endgame of an FP game with 1

phases, you can expect it to last 3 wks. Set it to 1.5

or 2

phases - and you really need that in order to get enough time to do a good job with press - and you're looking at a month to a month and a half. Add in the inevitable pause requests because you're juggling seven busy schedules for 4-6 wks and it's not at all unheard of for a game to last two months. I'm in one that's just eclipsed the three-month mark, and there's been 10 years in-game. And sure, that adds more time for negotiations... sort of. The average time per turn goes up, but since it's extended due to pauses, it's kind of a bad-faith effort to continue negotiating while someone needs a pause (and thus can't negotiate effectively)... and even if you're okay with that (most people are, I think), the time is distributed unevenly around particular turns determined by stuff outside the game.
TL;DR, much like this post, FP games are time-consuming and go nowhere fast compared to gunboat games. The social interaction in FP games is obviously a strong sell, but it really is a big time sink and if you don't have the time, gunboat provides an avenue for playing Diplomacy without the heavy time investment.