Yet Kagi is one of the very very few services I've seen that sends a monthly reminder that they are ABOUT to charge you... And you have time to stop it. Typically I only ever see something like that with shipped goods where they might have to deal with a return + cancellation

People also forget that they're subscribed to something (or that they signed up for emails either explicitly or implicitly), so they just report to Google (or whoever) as spam. I'm sure that's why I get a lot of email (mostly in my Gmail Promotions or Updates tabs that are from companies that scanned me at some event or whatever or I ordered something from.