Encryption, authentication, delivery notifications, read receipts, typing indicators, group messaging, hyperlink previews, third party app integrations, (some) emojis, etc.

The experience of using SMS is spartan and incomparable to modern messaging applications like iMessage, Whatsapp or Facebook Messenger.

Read receipts, typing indicators, delivery receipts, unlimited message size (text), better sending of media files and links to websites like previews)

Plus, if you lose your phone and you don't have your SMS msgs backed up, they are lost forever pretty much. With messenger, because they are not device dependent, they are still there. You can access them from any device (mobile or desktop) which is connected to the net.

I haven't used an SMS in ages...can't even remember the last time I texted or received one.