Yesterday, I wrote a script to retrieve MMS "easily" on the Pinephone (in the spirit of janky-mms [1] which does not work well on my phone and of which I'm unable to read the code properly), I need to take the time to release it at some point.
When I came to the US (mid 2010's), I was surprised a large number of people never even heard of WhatsApp.
But it never took off, I don't know of anyone using it. I must have received two in my whole life.
edit: I just checked. I can send MMS. This could have been useful. I sill send and receive SMS and I'd feel like I wouldn't try to send an MMS out of fear of the other side not getting it.
edit 2: ah, looks like it doesn't deliver. shrug