Honestly, no one knew Billie wasn't alright during the trilogy era. Irving Plaza is awful to watch now but at the time he was praised for just being "on fire" and the show as one of their best. In hindsight everyone thinks they knew and granted, a few people did raise eyebrows at the surprise Reading appearance. It wasn't many though. He's said he wasn't alright in 1997, but he didn't look like he did in the trilogy era then. Seeing photos and knowing he's with certain people doesn't tell us anything. I still don't think anyone can be blamed for worrying but even if going further wasn't invasive, there's no point because unless he tells us, we won't know what's going on.
Edit: sorry Hermione, posted before I saw you'd said some of the same things