- It had a table of contents. You can list the contents of a ZIP file, or even extract individual files, without having to decompress the whole thing. (Which was a particularly big deal back in the 90s, when extracting a large archive would take a while.)

- You could update an archive in place. Not incredibly useful, but certainly nifty.

- It had support for multi-disk archives. Again, big deal in the 90s.

Finally, last but not least: it existed in the PC world. Ports of software between UNIX and PC systems were rare back then, and were made more difficult by the fact that the software would have to run in a segmented (16-bit) x86 environment.

This is the perfect answer. The fact that you could split zip files across several diskettes was huge.

And AT&T could go after you for stealing their Unix utility source code, who at the time had a huge legal department with a hell of a lot of lawyers.

Actually, that's second last. Last, but not least is that .tar.Z did not fit the 8.3 uppercase-only filename structure; nor did the Unix semantics that .Z was one sort of compression and .z another.

And even if you had a UNIX tar.z file, chances are the data would be in big endian, have UNIX line endings, and you'd have to do all kinds of wizardry to use the file on a PC running DOS/Windows

Let me add ZIP2EXE for self-extracting archives.

I imagine it was just a product of UNIX/academia being somewhat isolated from the general public/BBS world. Before GNU/Linux basically nobody using PCs had access to UNIX-like systems, and probably wouldn't have known of tar's existence.

My older sibling exposed me to tar indirectly by granting me access to their university-provided dialup UNIX account where they ran `elm` for email access, and this happened long after I had been using BBSs for years with my PC.

Never saw a tar file in all my years of PC-based BBS usage. GNU/Linux and Freebsd are largely responsible for the general public accessing *NIX-like systems. BBSs (and their file sharing) were a thing before those existed.

Actually, plenty of people had access to UNIX-like systems. There was XENIX, for example, described by some histories as "the most widely installed base of any Unix distribution" of its time.

XENIX is too often forgotten, as is the fact that the Unix world had its "archiver wars", too. In this case it was tar versus cpio, with the POSIX standardization effort settling on "pax", the pun in whose name is reportedly not a coincidence.

The whole mainframe world was massively insular, and thus the micro/PC world basically had to invent gunpowder all over again. You can see it play out too this day.

PKZIP was a msdos oriented format (in the pre windows 98 era) and used extensively by millions of people who never saw a tar file. Long before windows 95 shipped, even. If you had a dos PC running 3.3,4.10 or 5.0 it was the near defacto choice.

One thing I don't see mentioned, though the other reasons are fairly valid -- the 'deflate' compression that was actually a non-backwards compatible update to PKZIP was superior to 'compress' -- gzip uses it, though not the PKZIP format.

There was for a good while a bit of a "compression arms race" with folks looking to find the most optimal compression to save precious time on BBS dial-up. For a while 'ZIP' won, then 'ARJ' managed to squeeze out a bit more, and so on -- though I think diminishing returns kept things from going too far beyond ZIP/ARJ on many BBSes.

In the early/mid 90s I remember looking pretty hard for a tar utility for dos and never found one.