So why didn't SYLK files get their own extension? Having to parse the file to figure out what it is? Seems so error prone. But maybe Machine learning will solve this too. Isn't that why extensions were invented- to reduce cognitive load?
They got, but many systems that produced them didn't have such a thing as a filename extension. Microsoft Multiplan, for example, ran on Commodore 64, CP/M, TRS-80, etc. (https://en.m.wikipedia.org/wiki/Multiplan)
And even if they did, chances were that transporting the file between machines (no, you couldn't move a floppy disk between machines, even if both machines had a floppy disk. Typical transport involved sending data over a serial line that only guaranteed to transfer 7 bits/byte, another reason why SYLK is ASCII) lost the extension.
