I see a few reasons:
Depth of field: Producer/mixer Tchad Blake seems to favour a blend of lofi/hifi-sounds in a mix because he finds it more interesting and fascinating. I also see a possibility in lofi to allow focus to specific sounds while others are allowed to blur in the background. There’s some Bob Dylan quote from when he’s listening to a mix and he turns to the engineer and say: “Man, you messed up. You can hear everything.”
Gel: Noise/hiss can also gel a mix together. Make it less sterile.
Messy is interesting: I just finished the book Messy by Tim Harford. Funnily, it’s sold with different subtitles: “The Power of Disorder to Transform Our Lives” and " How to Be Creative and Resilient in a Tidy-Minded World. I really appreciated it. In the end it discussed playgrounds for children, and how children often will turn down the neat and orderly playgrounds and prefer the danger and chaos of a nearby building site etc. Listening to the early demos of Jai Paul the other day I figured it was exactly the messiness and creative exploration that made them so appealing.
The magic of potential: There’s that mixing advice that we should sometimes leave the studio and listen to a mix from another room. Sometimes we can’t see the forest for the trees etc. A powerful tune always seemed to come through even on a lousy fm-radio with a weak signal coming in. In the same way demos can be more fascinating than the finished piece. It’s like the half-finished leaves something for the listener to imagine.
Wabi-sabi: The perfect imperfection. In a world of AI, autotune and cheap gloss error and clumsiness will soon be our way to stay human and interesting.
… and of course it’s always an esthetic choice, as well as a tradition.