Normally, when one's browsing one of the forums, one can see an "All" button to click on, to read an entire thread on one page (assuming it's not gone on for over 700 pages, which some have). I noticed it's not there today.
Well, it's a bit of both. It's clear that some people didn't use it or notice it (or want it), but I did. I'd use it sometimes when I saw a new large thread that I hadn't read before. I used it most when I had simply skimmed a thread before, then something caught my eye or I realized I missed something, and I wanted to give the thread a complete read again.
I'll have to try the ZO6 and blupupher suggestions. I probably used it once per visit.