The Reason?
Unlimited forts allows a player to sort out any mistakes. With adjacent / chained - you have 1 fort to make, so you had better make it count. I feel that Elite players should be at a standard where they don't require to undo all the mistakes. (just my opinion)
With 1 fort you are limiting the amount information you need to process in your brain. I guess thinking thru every fort and possible deviations for the future 1-2 turns is not for everybody
And you mentioned the mistakes people do, and having ability to correct them. It is not about errors u need to correct, it is about the frigging dice u need to correct. Unless u are attacking 10vs1, u can never be sure (actually recently even my 10vs1 have failed...). And u do need to correct it.
And how would u get 10vs1 in first place in the chained? Oh, wait i know, sit out or deadbeat for 3 rounds.
But the problem with the Risk is, that statistically attackers win (attacking with 3vs1 or 3vs2), so if you are going to sit out/deadbeat, and dice behaves randomly, as it should, you will lose your games.
And now about escalating. Playing in 6 peoples game (unless it triples) at least 2 players will either go crazy attacking (3vs3, 1vs2, 2vs2) or dice will screw them over and they lose all theirs armies by round 3-4. And almost in all of them someone gets to eliminate that guy. And that elimination is a way too random: have u been placed originally next to those guys? Are you making turn when elimination is feasible? So someone (quite randomly) ends up with extra 2-3 cards, and that is a huge difference for the round 4-5-6.
In triples u at least have 50+% chance that these 2-3 cards will end up in your team, so it's not that bigger deal.
Playing no cards requires most thinking, and it tends to take much longer time span, and therefore they are less entertaining.
That's my opinion, and explanation for my vote.