Why? Because the people who shop that way -- looking at everything, and especially hunting for a bunch of stuff by the same author to buy all at once -- tend to be people who visit a bookstore once or twice a year, in which time the turnover will be high. For those visiting once or twice a month, they've already seen everything except what arrived the last week or two. It's extremely tedious when you have to dredge the whole damn place every time looking for a needle in a haystack, even if you love books.
We complained. I pointed out that if you make a bookstore unappealing to me, that is painfully bad service. But it also means the store no longer appeals to major bookworms, that so many have quit coming it means the remaining customers are dabblers who apparently like it this way. I pointed that out too. But it's probably far too late to fix.
*sigh* The past is a foreign country, and right now I'm homesick for when bookstores were soft quiet places full of BOOKS and didn't come with a hunk of electronics literally blocking the path into the store so it has to be sidled around.