Aizawa is an omega and the daily wear of his capture scarf and constant use of his sleeping bag are impulses caused by the repression of his nesting instinct when he was young.
No cause why is this concept so good???
I don't know if you've ever seen the theories about him coming from a wealthy background, but I feel like that would work so well with this.
We don't know much about Shouta's family but I tend to imagine that they neglected him in favour of their socialite lives. When they were around, they were still distant, leaving a clear divide between Shouta and his parents. They pushed him, trained him, to be a certain way and fit with their lifestyle despite how reduntant and meaningless Shouta thought it all was. Their lack of care and emotional support could be one of the reasons he struggles so much.
But if you throw a/b/o into the mix too, you get a whole other wave of hurt. This means that not only did his family neglect him but they also went so far as to actively try and train his instincts out of him. Including instinct supressors and blockers from a young age. This would have left him uneducated, underdeveloped and unaware. Three very dangerous things to be in a world where dynamics rule. He would've been in a vulnerable position for most of his youth and it isn't until he starts getting older and training to be a hero at school that he's taken aside and properly taught about the secondary genders and how they affect people. I can imagine so many different scenarios of Hizashi and Oboro helping Shouta on his journey to finally feel and master his instincts for the first time.
The constant full body coverage and enclosed sleeping spaces (such as his sleeping bag) to mimic instinctual comfort and nesting are just the perfectly angsty cherries on top.