Apple appears to have made a significant change at some point to how some standalone (not with a purchase or upgrade!) iPhone trade-ins work. I haven't seen this covered elsewhere. It used to be that Apple would either automatically send a trade-in kit or you could easily request it by clicking a button. Now, Apple says that if you want the kit, you have to call customer support to specifically request it. Apple won't even provide it via iMessage support, you literally have to get on the phone and wait on hold if you want the kit. That's some egregious dark pattern nonsense, like trying to cancel a newspaper subscription. They're just intentionally making it more difficult to use this convenient option.

Edit: per the discussion below, it looks like this policy change applies to some (but not all) standalone trade-ins for Apple credit that you can use later, and not to other kinds of trade-ins (e.g., credit against a purchase that you're making at the same time or an upgrade). It also might only apply to certain types of devices. Updated the text above to reflect that. Still bad!

Edit 2: I don't quite understand why this is getting downvoted to oblivion. It's a real and user-hostile policy decision by Apple! Folks below confirm that they've had the same experience.

I received my iPhone 2 days ago, and the trade in kit hasnt been shipped yet. I got a UPS tracking number for it but it doesnt register as having been received.