One of the points that Douglas Wolk makes in Reading Comics about the way comics work has to do with imagination. He makes the (seemingly obvious, but worth looking into) point that in a comic book, the reader's mind has to fill in the information between each panel. This normally happens semi-automatically (or, once you've been reading comics long enough it does, anyway) but it's still a thing the reader has to do. They have to use their imagination in a particular wa to read comic books.
And then Wolk says this thing that I think is again obvious but worth stating: that using one's imagination is one of the purest pleasures around.
Now let's think for a moment about how threatened our poor audience's imagination is these days. How few outlets it has to really grow and be engaged. Let us take the ultimate in imagination-deprivation, the Reality TV Show. Now I enjoy Top Chef as much as the next guy, and watched the first seasons of The Apprentice and American Idol when they were on television, so this is not an eletist argument here. But still. As if it weren't enough that film and TV work in imagination-defying ways, aiming to be more and more "immersive" and "realistic", using locations instead of sets and various tricks meant to bypass a willing suspension of disbelief... we know have a very lucrative industry that involves not even demanding from its audience the imaginative leap of believing the people in front of them are in fact different people.
(Of course we as audience members might want to question why we're being asked to recondition ourselves not to use our imaginations. The first reason I can think of vis-a-vis TV has to do with Union Busting. Reality Television as a genre took off shortly after the threatened SAG strike a few years back. If the networks can convince us that we don't need to pretend that Martin Sheen is President Bartlet, then his labor becomes devalued and they don't have to pay him as much. But that's a post for a different time.)
Reality Television isn't the only assault on our imaginations, there are others that I'm sure we could all think of.
But what the more luddite arts can do (should they choose to) is actively engage the reader's imagination by demanding imaginative leaps as a precondition to approaching the art at hand. All art (Even TV and film-- those are 2D images you're staring at, after all) does this to some degree. TV and Film as a general rule try to find ways to bypass that imaginative circuit by simply convincing you that what you're watching is real-ish.
Comics engage the imagination inherently. Theatre does as well. But if you pay attention to either medium, you can see a fairly protracted debate about how exactly one should engage the imagination, and whether or not an artist should try to convince the reader or audience member that what they are seeing is real vs. asking the audience to make the imaginative leap that it is.
In comics we see this debate all the time. It is at the heart of James Kochalka's ideas of craft vs. cuteness. It's the reason why Alex Ross (not the music critic) who is able to far more realistically depict human beings than, say, Jeffery Brown is a terrible artist while Brown is a quite good one. Or why Joe Sacco's less realistic earlier art (in, say, Palestine) is more effective (although quite a bit uglier) than his hyper-real later work in The Fixer (althoug his writing has gotten better and he's still awesome). It is because Alex Ross (and later Joe Sacco) chip away at the pleasure of cooperating with the artist to immerse yourself in their world.
In theatre (as in TV and Film) we frequently try to bypass this demand of the audience through (for example) obeying certain rules of virisimilitude over stylization in design or by creating stylistic conventions in writing or performance that mean "this is real" when said conventions are in fact highly stylized and unrealistic. Rather than try to work with the audience to immerse them in the world we've created, we try to immerse ourselves back into theirs with, I would argue, diminishing artistic returns.
And I think audiences are hungry for this imaginative experience specifically because it is hard to get from other places. This is why I think The Lion King was so popular with critics despite the fact that it is overlong, frequently incoherent and based on not-great source material. It asked of its audience frequent imaginative engagement, and rewarded them for it. The opening procession of the show is incredibly beautiful, and it is beautiful in part because you as the audience are actively participating in creating it in your own mind.
The last thing I'll say about this is that this may very well be an advantage that lower budget theatre has over higher budget theatre. Just something to think about...