If you saw any of the live seminars I've staged in the last decade, you've probably seen me reference CBGB's bathroom as everything great about rock and roll--and everything wrong with live performance venues.
Long before YouTube comments, there was CBGB's bathroom. As a visitor, it was your duty to leave more than just the usual deposit. Bands left stickers, artists added to an ongoing collage, and patrons scribbled with Sharpie--or worse. The collaboration just built up over time. The last time I visited, the walls were so encrusted with contributions that I don't think you could have fit an actual person in there.
And as much as folks fondly remember a bathroom that represents the entire punk ethic of New York in the 1970s, it's that total lack of creature comfort that prevents many potential audience members from seeing (and enjoying) live music. As much as you want to believe that audiences are going to pack the place because of your awesome act, your listeners are often thinking about more mundane things, like the state of the bathroom.
It might not be cleanliness, it might be space, or lighting, or some other element that's entirely out of your control. But where you play is part of your band's brand. Staging a gig at someplace where your audience's creature comforts are in question gives your prospective fans another reason to tune out.
Don't believe me? Artist Justin Lowe announced his intention to recreate CBGB's bathroom during an installation at Hartford's Wadsworth Atheneum. If you never visited the original, you haven't been inoculated by nostalgia. I dare you to spend 90 seconds in there without thinking about whether you may need rabies shots.