"The Story of O" - what's up with the fashion (or lack thereof)?

Okay, so I finally watched "The Story of O" (1975)... and wow. It's... something. I went in knowing it was gonna be intense but honestly, I was half-expecting some elaborate, almost theatrical costuming, you know? Given the, uh, subject matter. Instead, it was mostly just... nothing. Or simple negligees. Like, I get it. It's about stripping away identity and control, blah blah. But still! Even the settings felt so… bare. I was hoping for some decadent silks, maybe some interesting historical references even if they weren't accurate. Rene always looked sharp though - did anyone else notice that? Was that intentional, the contrast? I'm probably overthinking it, but as a fashion person things like that always jump out at me. He's the only one with any real style. Did anyone else find the lack of visual extravagance kinda... odd? Maybe it was a budget thing? Or maybe it's just too on the nose – like, "look, she has nothing, get it?!" I have so many questions. Anyone have any insight? I'm dying to know if there's a deeper meaning behind the minimalist wardrobe choices, even if it's just a cop-out.