Maybe because tech-savvy people understand the need and importance of encryption? There's of course always the exceptions that say they don't care about privacy, but that is fortunately usually a small group, at least in the tech-savvy world.
Both tech savvies and laypeople expect private/encrypted messaging app to provide the basic property that only the sender and the intended recipients can read it. This is achieved with end-to-end encryption. Techies know the term, and can understand it's not present. Non-tech people don't understand, and just rely on word-of-mouth that it's super secure, when it's not.
