I'm not suggesting any change to the length of short rests or the nature of short rests. A short rest is an hour. That's really no more or less RAW than saying, "An hour long short rest tacked onto another hour long short rest is actually just one short rest, because a short rest is defined by being 'no less than one hour.'" And, as you say, the only reason for a party to take a short rest immediately or shortly after another short rest is so that the fighter can recharge the second wind feature. It's the only short rest feature I can think of that has utility beyond immediately facing danger. (Well, maybe the warlock casts a minor utility spell and then wants to rest for another hour? Some sort of scrying spell? I don't know their spell list off hand.)
But what if the fighter is the only one really hurting, the party has no healing potions, scrolls or other healing options, and they want to press on? They decide that they're more concerned about what is waiting at the other end of the castle than whatever is wandering through the hallways they're currently camped in. They say, "alright, we're gonna risk it and take another short rest, all for a measly 1d10+character level hp for our fighter." That's a decision with risks. Why not let them take it? You don't need to regularly roll wandering monster checks to just say, "man, these guys stayed here a lot longer than might have been prudent. Let's roll a die and see if they get lucky."
Suggesting 2 short rests per day (for the sake of adventure and encounter planning) isn't the same thing as mandating it. I think, wherever reasonable, player choices should be governed by risks and rewards, not DM (or PHB or DMG) fiat. The rewards for 2 consecutive short rests are very low, but, under the right circumstances, they might be worth it.
(I would also accept that this is not "reasonable" in a game where the DM does not run unplanned encounters. If a session really does follow a fairly scripted series of encounters which the DM has planned beforehand, it is unkind to the DM to impose consecutive short rests on that DM, because now he has the choice of stepping way outside his DM comfort zone and play style, or giving the players free hp, because he and his players absolutely hate wandering monsters. In that case, Rules as Fun would dictate that the DM and the players come to an agreement of, "you don't run this play so I don't have to drop a band of wandering monsters on your ass, which you know you and I will both hate." It's like limiting blitzes in touch football, because it's not fun to blitz when the offense can't really block.)