>The books are often not available at all in the region you’re in or if they are, they might be priced differently.
Also, "the region you're in" can even mean the same country as the publisher, or even anywhere in the world. Publishers may be unwilling to sell the books to individuals at all, or may sell them only as part of larger sets with very high prices. They may only be willing to sell hardcover copies, for a premium, even if they do produce softcover ones. It's simply not feasible, in most cases, to purchase the books you need to do scholarly research as an individual. And if you're looking at digital publications, the situation becomes even worse.
I recently had someone tell me that their father, in the US, had been looking, not wanting to ask them, for a copy of a book they had just published a chapter in. The book could only be purchased by individuals as a set of six books, all in hardcover, for around $500.
Part of the problem here is that individuals are often not the target customers for academic publishing: libraries are. Publishers can be worried that if they do sell in ways that are convenient to individuals, that might reduce their profits from libraries. If they sell books individually, instead of as larger sets, then university libraries can order only the volumes that people request, rather than needing to purchase all of them. If they sell softcover copies, libraries can buy them and rebind them in-house, or simply have them as softcover, rather than needing to pay that premium. If they have prices that are reasonable for individuals choosing books to buy with their own money, the prices will need to be far lower than what they can be for libraries being instructed to buy books by others and needing to figure out how.
And, as you mention, the journal (and reference) side is even worse. Outside of very high profile journals, which are simply expensive for individual subscriptions, many otherwise quite reasonable journals from reputable publishers simply won't offer subscriptions to individuals at all: their only option for individuals may well be article-level purchases at prices that would be utterly absurd for actual research. In some cases, they also won't offer subscriptions to institutions, except as a (potentially very large) package of journals. At a small university, I can remember the library pointing out that getting access to one yearly proceedings publication very important for our field would cost a five figure yearly amount per year, because it was only sold as a package of hundreds of publications. Larger universities can have problems with this in the six or seven figures.