My personal headcanon is that since Valla is 1) and underground kingdom and 2) riddled with curses & magic, Vallites physically loathe the mere thought of anything being between them and the bare ground. Which is why Corrin & Azura are both barefoot, the one time they managed to force Corrin in boots they spent the following hour screaming nonstop because this is Uncomfortable and a Very Bad Sensation and they wanted it to Stop. That is also why, of all things, Corrin recoils at the Hoshidian throne; the problem isn’t that Queen Mikoto suspects them of being a traitor, nor a trust problem, it’s that the throne is too high and if Corrin sat on it they wouldn’t be touching the ground anymore.