You'd probably have to ask them! Maybe they said PDZ at home before arriving?

I don't think "no one" is a fair statement; many people do.

@racquetball I too have seen many places where the overwhelming majority of participants are careful about this. Assertions otherwise won't really do much to convince those who have seen this with their own eyes. I would recommend modifying the question to be more specific to avoid further downvotes, which people clearly feel are warranted. Perhaps a focus on possible leniencies would make for a better question.

@רבות מחשבות what leniencies? There are none. It is a black and white halacha in Shulchan Aruch.

I used to daven in a shul which had no talking at all. It simply wasn't tolerated. And the people who attended bought in to that and held fast to the rule. I took it on myself not to talk during davening, beginning to end. I don't always stick to that, but I do often. The absolute nature of the claim in the question (and the strident response to counter claims) is problematic.

The question as asked isn't really answerable as every person or place is different so how can we know why (or even if) they do this