they have only one side and no volume!

I'm more of an infinite volume half full kind of optimist myself.

well, i'm aware of that actually. still don't get it. you look at it, realize this thing exists and that's it afaiac

People look at beautiful sunrises that way too, sometimes

Some people just have good taste. You apparently are not one. Do you look at an Escher piece and think what's so fascinating too?

That's an unnecessary insult to what could well be an honest question.

Trying to explain is dodgy - it never works for jokes, either. But I think they represent a bundle of interesting contrasts that hits a sweet spot for a lot of us. Most people have made a Mobius strip out of ephemeral paper and thrown it away after fiddling with it; these are hard-wrought, complex artisinal craftings from the same family of ideas. The idea of "Klein bottle art" at first sounds rigid and limited, but the variation shows lovely creativity and artistic sense. They riff off the low humor of a dribble glass by mixing it with the sophistication of advanced math. The artist stays down-to-earth and accessible, even though he's clearly walked quite a way down a particular road of practice and experimentation that the rest of us are only going to admire from afar.

because physical embeddings of mathematical concepts are quite enjoyable to nerds and others.

You probably wouldn't also see anything interesting here (Henry Segerman http://www.3dprintmath.com/ or even https://www.mojoptix.com/2015/10/25/mojoptix-001-digital-sun...

Personally, I can't visualize things in my head easily but having a physical object I can hold/rotate/inspect helps a ton