Because when I click on all replies and hen try to expand a thread to see everything in that conversation, it's not all showing up.
For example, I want to read all the replies in a thread that says there are 272 more replies. I click to show all of those but the total in the thread is only 105 replies. In fact, I have been flowing this thread for some time today, and at first when the number of replies increased there were actually more replies to read. Now the number keeps going up, by over 100 replies, but there are no more replies to read that I have not already seen.