It's not all about profit as European SMS is now free. It is however about decentralisation stifling feature development - a trap we run into again and again, from email to IRC to SMS to Fediverse/ATProto.
WhatsApp is one company so if they want to enable sending images they can just do it, and they don't have to coordinate with anyone else. MMS was a failure because you couldn't be sure if your recipient would actually get it, or if your carrier would actually let you send it.
WhatsApp is one company so if they want to enable sending images they can just do it, and they don't have to coordinate with anyone else. MMS was a failure because you couldn't be sure if your recipient would actually get it, or if your carrier would actually let you send it.