This is absolutely true and a perfectly fair challenge. There are very few books on banking operations. Most businesses tend to fall somewhere into the enterprise continuum from foundation architectures through to organisation architectures and each such organisation, even in the same domain, is different. Banking still has it tough due to the overlapping and often competing regulatory contexts in which they operate. Hence, I’d argue the ability to write a book on banking operations would be impossible for someone who isn’t a generalist, yet there are many books in individual regulatory compliance, financial calculus etc. as you say and banks generally don’t like generalists.
I’d argue your point on using a domain of knowledge falls into this quite well though, since each bounded context bounds exactly a domain. I’d be interested to know more about the writing and teaching approach you’d like to see though. Part of banking’s limitations is it’s opaqueness, for many reasons. That may be a big thing to overcome, but I think it’s doable.
That said, my counter is can you find a problem in banking that can’t be formulated mathematically?