In at least some areas, books that are easy to understand are not hard to find -- but they're usually not the same as the books that are right. If a student wants a book recommendation, I'll be much more inclined to offer a book that's correct almost everywhere over one that's simpler but will give them enticingly incorrect notions that are harder to correct later.
Teachers are people, too, and may often themselves prefer an easier source to understand, other things being equal. Certainly a resource should be as simple as possible, but no simpler.
Which is to say, what unskilled students would prefer to be given and what an expert in the subject believes would be better for them to have (albeit requiring more effort) are not always going to be the same thing.
My own subject area has a lot of "amateur" users in other subject areas - many of whom go on to write textbooks on it aimed at students in their own area of learning. While some of these out-of-area writers are widely read and highly skilled, many are not. Many of the textbooks that are written in such areas try very hard to make the basic knowledge of this out-of-their-area subject less technical/"easier" for the students.
Some of these books are extremely popular with students and teachers in their specific application area, gathering huge numbers of sales across many editions. Unfortunately, some of them are also quite brim-full of nonsense, and the ability to distinguish superficially plausible nonsense from the slightly less intuitive fact is fairly widely lacking; even when better books exist they may fail to generate much traction.
I try to point people toward "better" books, but it's not always successful.
One thing I have often told students is to use more than one book; it's not always the first book you look at that's the best one for you individually to learn from, and an additional source can provide useful perspective a single view loses. For my own learning, with a topic I'm unfamiliar with, I tend to start with looking through a wide selection of sources (if so many are to be had) before narrowing it down to a few to work from.