Interesting thread. Don't know why I didn't see it since that is one of my favorite Clapton songs. And while I'm not really understanding the point of the question, as to the Reason he did this, I'm surprised that most don't mention the most obvious reason:

AGE. And hearing.

Townsend is nearly deaf. Most of the guys of those big loud days of blazing guitars are all suffering hearing loss and other health reasons. Sitting with an acoustic is much easier to control and has them concentrate on more nuances of the songs themselves, the finer aspects of playing, and a more age appropriate role as elder statesmen of their art. And while they still play some electric, the reason for the "unplugged" approach was also because their FANS WERE OLDER. The ticket prices were going to be more and it was honestly easier on the ears of the people paying the bills.

It also was a way to repackage their material to maintain the "nostalgia" effect, while introducing it to a new era of fans. The two Layla;'s were both distinctive and yet both different. Same thing. And as Clapton got back into a more traditional blues phase, he was getting back to the roots of Robert Johnson and the old players who played acoustic in the 20's and 30's.

Then, yes there is the "boredom" factor. Every artist, with the exception probably of Jagger and the Stones, go through a period where they are just "solo'd out." How many notes can you play? And as the "shredder effect" starting in the 80's and onto today, when you can't stand up note for note with the younger guys and gals, why try. I watch YOU TUBE videos of 8 and 9 year olds ripping off the Eddie Van Halen stuff, and playing so many notes, it gets boring very quickly. Even played with an 13 year old recently, and while he could play a bunch of notes, was about as inauthentic as they come.

So I'd say this is just a part of getting older and more nuanced in what you do as an artist. When you are young it's all about speed and flash. When you are older its' about nuance and longevity. The answer to me is easy.

He's older. We all are.

MAB