That's because at the time with the information that is available there is usually only one right opinion. It doesn't do much good to share an opinion in the moment that downplays something for a future date that may never come, if you feel like you want to wait to have an opinion you can do that but I don't know what kind of discussion it is to post it.
Like if it comes out someone allegedly did a racist thing, and the whole thread is talking about how racism sucks and talking about how they are effected by it and sharing those perspectives, and saying they are disappointed with the person, someone jumping in to say "I dunno, just going to wait for the facts or more info" could be seen as kind of pointless at best and dismissive of ongoing discussion at worst.
And, I bet I could find plenty of times where people said they wanted to wait for more info and no action was taken. It can very much depend on the topic.
Edit: And I'm not dismissing you entirely or anything, you could be right, that's just my take on it but I don't want to turn this into a meta shitshow, I think if people have issues with the site they should interface with the people who have the ability to change it, not just throw it out into a thread where it's possible nobody will even see it just becomes an unconstructive gripefest based on feelings with nobody bringing forth data to prove their position.
Nah it's entirely reasonable to say "lets wait for more information." It's the foundation of all first-world justice systems. The highlighted sentence would entirely justify blaming Depp for all abuse a few months ago "based on all information available at the time."