Not in my experience. 100% of people I know that have it, also have read it. We buy that because we're Tolkien nerds. People who don't want to read it don't buy it. Also it's not at all like yellow pages for looking stuff up, it's more like the Bible I guess, a collection of mythological tales of old.
I guess there are some people that have inherited it, or just bought it for collecting, but I don't think this is the main case.
It might be different for The History of Middle Earth, it's huge and requires a lot of time, and it's more yellow pagey as far as I understand. I have them but have not read much of it yet. (Maybe you meant these?)
I rarely check people’s bookshelves but my experience has also been that people either don’t even know what it’s really about or they absolutely love it.
But I guess it’s possible that some people buy it after reading LotR expecting more of the same and then give up after reading the first few pages of the Ainulindalë.
There is not much statistical evidence for my statement. Mostly from the people I know (though one actually read it, she is a true nerd) and myself (tried it but am probably not as much a middle earth fan as I thought)
Strong disagree. I've read The Silmarillion. Sure I don't remember much of it now, but at the time it was interesting and entertaining to me. It's also not that huge a book, on the same order as one or two of the main LoTR books. If the KJV were in the same (normal) font size+width and paper thickness it would be Gigantic.