Messages
Why can’t I delete all when I go to recent messages of my 100,000 messages?
iPhone 11, iOS 16
Because that isn’t a feature of iOS. From the list view you can tap the circle with 3 dots, then Select Messages, and check off a bunch of message threads at a time and delete them, but there is no “select all” or “delete all” function.
You won’t get an answer from Apple here, as this is a user-to-user forum, with minimal Apple participation. Sounds like a good idea, but the best place to suggest something to Apple is here→Product Feedback - Apple