I have a feeling like many of the apps are reading the clipboard on the launch because they probably act on copied text (e.g. if it's a link or a number, they can use that to show a suggested user action).

Obviously I might be wrong, but we live in times where many applications are reverse engineered and their traffic is MITM'ed all the time. I'm not sure if anyone’s sending those clipboard contents outside the device. That would be a problem.