[harpratap]

Your argument fails when you consider Whatsapp - the biggest messaging platform, where you need to add people's number in your contact to be able to see their names.

I agree with power of defaults though. Only reason iMessage took off, and so did other Apple services.

[mjmasn]

You definitely don't... Unknown contacts show as e.g. "[phone] ~Bob" (their WhatsApp display name). When you save them to your contacts it switches to the name you added instead.