They already have an end-to-end encrypted messaging application: it's called WhatsApp. I have seen so many people (and have myself been) bitten by WhatsApp's E2E implementation: messages lost because your phone was barely online and you "read" the message but didn't fully receive it, leaving you to awkwardly ask people to re-send things. Plus the constant need to backup your messages because if you don't you can lose access to them forever. Plenty of my family have lost messages/images that were sent to them and were important to them.
I'd rather not deal with this. Sometimes I want all my messages to be stored on a big company's servers. They should at least give people the option to choose.