Hello; I guess because it is a thread in the lounge and, although pointless, does not appear to break any rules it will have to be endured.
When there are several photos it slows the loading of a page way down. Because of this I unfollowed all-happy a while back. Some days there are only one or two posts on an entire page. From time to time I open the unfollowed content to see if all-happy is doing something other than the random pictures, not so far.
As others have asked, I would like to know why this is being done. My take so far is that it is a way to mess with lounge threads without breaking any rules.
Kind of reminds me of the way folks use to play music on the CB radio, sometimes overriding all other conversation. CB' s are much less popular now days so it is easier to get useful road info.