It seems natural to spend a little time exploring the interface of an extremely complicated instrument that is an integral part of your daily life, reading Tips, etc. That also means if this device is not exactly that heavily used (say you have assistants for that), you are spared of wasting your cognition cycles on simply being aware about all the features it has in store.

FWIW search field in Apple’s own apps like Settings mentioned upthread is revealed to me every time I scroll from the bottom back up to the top of the list due to inertia, I don’t know if they changed it recently or not. (Other apps often make a mess of the same UI pattern. In WhatsApp it is much more difficult to discover, requiring to really pull down and wait to see Archived Chats, and meanwhile Search field is just there wasting screen space despite being used once every few months.)

That said, I don’t have a strong opinion about message timestamps in particular—I believe there are ways of showing them smartly if you haven’t used your phone for a while and missed a bunch of messages without overloading the UI for people like me who couldn’t really care less about that (RIP my IRL social life as of late). Perhaps Messages could use more attention from a good product designer.