I was involved in those decisions. The people I worked for knew their businesses and knew the importance of cash flow to it. It had a lot to do with capital.

The simple equation was that setting up a network did not look like it would make those companies money. And in the Windows for Workgroups era, running CAD on Windows was a massive performance hit.

Don’t ignore the capital cost of buying Windows versions of Cad software…potentially thousands of dollars per seat. Don’t ignore the cost of graphics cards…the high performance card might not have Windows drivers and every machine might have a different card bought at a different time.

And don’t ignore the cost of a file server that inspires confidence. In an environment where contracts are five to seven figures, the local PC repair shop is not the most enticing risk.

You don’t need Windows for networking. There was lots of networking software for DOS. NetWare was the most popular, but there were heaps of alternatives: Microsoft/IBM LAN Manager, Banyan VINES, DEC Pathworks, Sun PC-NFS - most of those required a server running some other operating system (such as OS/2, Unix or OpenVMS), but there was also a category of “peer-to-peer” DOS networking software which could operate without a dedicated server, e.g. Artisoft LANtastic, Novell’s NetWare Lite and its successor Personal NetWare

So what it comes down to is: The handful of places you worked in a specific industry didn’t want to spring for some ethernet cards, and so therefore office LANs were uncommon?