These are not real readers. Reading books in the past was a very minority activity. There are more literate people today, but not all read books. If you look at books 50 years ago they were smaller. On average maybe half the size.
Ray, it was a joke on my part.
Of course, everything you said is true, I don't argue that.
However, every joke is only partially a joke. I can't but admit that, being used to reading long novels, I sometime notice that I can't finish reading a long article because I become tired with it. Several of my friends (well over thirty and forty) admitted the same thing. In the end, the Internet influences everyone.
And yet there are people whose jobs it is to pluck out a manuscript among hundreds and decide to spend a bunch of money to publish and market it in the hopes of turning a profit.
Ah, here is the key point: money and profit. However, this point I don't intend to discuss as it would be completely off topic here.
The reason genres exist at all is because readers tend to have expectations
I have to strongly disagree. Genres exists only because it's easier for publishers to sold books with tags glued on them. It can be proved by a very simple fact: there are different genre system in different countries, so the classification adopted in the US, for example, is incomprehensible for readers on my distant planet, and vice versa.
Did you read 'Tomminockers' by Stephen King? What is it - SF or a mystic thriller? Meanwhile, it's one of the best King's books.
Tastes and expectations do change in a population over time.
True. The problem is, no one really knows those tastes and expectations. We have only statements made by book publishers and the publishing policies they follow, nothing more. Even worse, publishers often try to form those tastes to make bigger profit.