Programs that do not comply cannot talk to each other, and that appears to be all the pressure needed. Unfortunately, there are instances where companies decide that proprietary solutions are preferable to standards-based solutions. If you use a proprietary piece of software, it may be able to do things that are not in any standard. But it will only be able to do these things with other programs from the same vendor. Proprietary solutions are often touted as containing features that other software does not have.
Standards often lag behind the introduction of new features.
Uuencode and Mac's binhex are examples. These methods worked well if the recipient had the same software you did. But without standards there could be no guarantees that the material you attached could be read at the other end. Some programs continue to give you choices regarding the method of attaching non-text material. It is the most likely method to be correctly decoded at your message's destination.