I hate how in iMessage (it's always been this way) if you ever send someone a photo, video, gif, sticker, meme, etc. that you have previously sent to them, the phone re-uploads the file and sends it through again. On cell coverage it's a lot slower and more redundant than if iMessage noticed that you've sent something before and simply makes it pop up as new on the other person's device without actually having to transmit the file again.
Also, it takes up more storage when you are sending files twice.
Also, it takes up more storage when you are sending files twice.