True, but the question is about whether it is reasonable to infer someone is doing criminal things from their use of an encrypted messaging app. I don't use Signal so that police can't read my messages, I use it because it is good security practice to be sure that the only person who can read messages from me is the person I intend. If my partner and I are talking about private things that is our business, nobody else's, and if i use something like standard SMS to have that conversation it is out in the open for anyone to skin and see. I wouldn't want anyone looking in my underwear drawer, not because I have hidden drugs in there, just because it is private and not anyone else's business.