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.
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.