Why have they been so successful? Why didn't MMS 6.0 implement everything that exists in modern chat applications. Why is Meta anything more than the anonymous humble entities producing sms and "phone" apps?
MMS still don't work reliably for me (lost a message just last week that someone swear to have sent). And for a long time they were not free as well.
The difference is that MMS/SMS is standardized and agnostic to the client interface. While WhatsApp is proprietary and monopolizes the client.
We could easily have had a "internet direct message" standard implementing most of WhatsApps features. (Wait... Isn't that SMTP?)
Maybe I'm just ignorant, but what does WhatsApp bring that let's say email++ does not have?
... actually that's still the case in varying degrees and locations. And once you've got great market penetration in an area, there's little to no reason to switch unless the competition is noticeably better, which MMS really has no claim to.
Open standards hadn't.
Or if you're referring to MMS: insane user cost and insane unreliability, standards mean nothing if the implementations are all trash.
Not saying it should have, just that I don't really see the difference in functionality.