What is so special about prog?

There was a thread on Progressive Ears the other day which piqued my interest. I suppose it was a variation on the 'what is prog?' threads, which are beyond tedious, but it got me thinking about what sets 'prog' apart from other genres.

The thread was initiated by 'Homburg' who stated:

I've been listening to a lot of classical and jazz lately. It would be easy for me to dismiss prog as relatively unsophisticated, yet I keep returning to it, whereas I return to other forms of rock increasingly rarely.

There have been a lot of rock bands (e.g. Talking Heads, U2, REM) who are just as intelligent as the smarter prog bands, so what is it that makes prog special for us?

Surprisingly, a lot of responses were dismissive of the premise of the thread:

Myself, I find nothing special about it. There are a few songs here and there that I can get into, but not many. Still trying to research and find some other tunes I can get interested in. Seems a losing scenario, though. (Gruno)

Prog hasn't been "special" for many, many years for me. The old stuff from the 70s is still special, but the whole "scene" (the 3rd Wave, internet, etc.) that started in the late 90s (for me) stopped being special 6-7 years ago. (Vic2002)

Absolutely Nothing! Only prog fans think it is special. Prog is no more or less special than any other genre. (Stoneage dinosaurs)

Responses of this nature made others wonder why the authors frequented a progressive rock forum.

Some of the other answers were lighthearted:

But seriously.....I've analyzed this situation thoroughly, and at great length, and have come to the conclusion that it is multiple-necked stringed instruments. That is what is so special about Prog. Especially if you've got a 12 string joined to a bass, that gets extra prog points. (WideOpenEars)

...while other respondents did attempt a serious answer:

The extended songs are the key. I cannot get enough satisfaction of a 3 minute song. I need development, breaks, changes in tempo/key...and it should still be rock music. (Soul Dreamer)

...and Homburg returned to add his own explanation:

I think it's the texture I find so pleasing: rock guitar alongside classical-style piano, melodies and complex rhythms, harshness and delicacy, flippancy and grandeur. Hard to emcompass in three-minute songs yes.

For me, Soul Dreamer's and Homburg's answers are about right. Bearing in mind that music from so many other genres is just as, or more, sophisticated or complex than prog and that technical proficiency isn't peculiar to progressive music, it clearly isn't special because it is 'superior' in any way.

I enjoy good songs and tunes but also like instrumental music, so prog has the right balance; more so than other genres. I also like music and words that connect on an emotional level and, again, the best prog ticks that box, when some other genres don't. And prog is also better than most genres at dynamic variation - from quiet moments to powerful grandiose sections within the same track.
I can, of course, get the tunes and the emotion from lots of music, but I'm often left wanting more if the instrumental sections and effective dynamic variations are lacking.

A good example of what I mean can be heard in the music of Elbow. On their most recent album, there is a beautiful song called Lippy Kids. Great lyrics and soundscape, lots of emotion.

But it fizzles out just when it should be gathering itself for a big dramatic conclusion and, when I listen to it, I end up thinking: 'why can't they let themselves go a bit more?'

Indeed, for want of a better word, I wonder if they'd reach even greater heights if they were just a bit more 'prog'?