Habituation is a necessity with polite formulae. I remember when I was still at the mechanical stage and had to pick apart phrases as simple as shitsumon sasete itadakemasenka- lessee sasete is causative so 'be made to/ allowed to' ask a question, plus itadaku- receive from a superior, which must be me 'cause it can't be them- in the potential form, can I receive- plus looks-like-a-negative but isn't: can I not, so: can I not receive (the favour of) being allowed to ask a question, ergo, 'mind if I ask?' whew.
You then go on to such everyday constructions as 'ashita o-jama sasete itadakimasu' tomorrow I will receive the favour of being allowed to bother you ie 'I'll call on you tomorrow;' and '(dareka-san no hanashi) yoku kikasete kureta' which untwisted means 'he often did me the favour of making me hear stories about dareka-san' ie 'I've heard so much about you.' As I say, hear it enough and it just becomes an instinct; and how lucky I was that my boss' office was right next to my classroom and I got to hear his telephone conversations.
Well, and then you come to the formal upper-level stuff that the 12K female immortals use about the kirin, which I'm not likely ever to have to use myself. Things like asobasu, which looks like one causative form of 'play, amuse' and which is another high-falutin' way of saying 'do' and occasionally a substitute for -nasai. Gomen asobase and so on. I imagine enough Taiga drama dealing with court ladies would drill this into you as fast as overheard telephone conversations but mph- I suffered through a few Genji specials and Kasuga-no-Tsubone and didn't understand a word. I'll take Konron no Tama instead, thanks.
Anyway, what I wonder about is good ol' Keiki and his instinctive high-level speech. He uses elevating forms even about the much-younger and clearly still immature Taiki. Japan-born Taiki calls himself boku, Japan-born Enki calls himself ore, Houzan-born and reared Keiki calls himself watashi. Kirin grow up on Houzan and see only their female demon-beasts and the immortal girls until they go find their king. Which means they never hear anyone using familiar forms, right? So do traditional kirin never use them at all? We never get any other kirin talking at length to find out.
The Immortals themselves say Keiki is overly formal, so he's obviously a bit too respectful even for a kirin; but where would he learn other differing levels from? And the thing that's always puzzled me, how would he learn to understand masculine common speech? I mean, nobody on Houzan uses it. Go from keigo verbs and forms to colloquial male and you're essentially speaking a different language, at least as different as Mississippi English is from Lancashire's. Possibly he never talks to any ordinary men... but suppose he's faced with the King of En-- then what does he do?