Indeed. In the early 90s, it wasn't necessarily obvious that everybody needed a TCP/IP stack. "The Internet" was still essentially academic, and something the average person didn't really know anything about. Small PC LANs typically ran on some combination of IPX/SPX and NetBIOS.
3.11 laid the foundations for modular Windows networking, but included TCP/IP support was two years away in Windows 95, and even then it still wasn't installed by default(!). Microsoft took a while to catch on.
http://en.wikipedia.org/wiki/Windows_3.1x#Windows_for_Workgr...
Also, for your historical needs http://www.trumpet.com.au/index.php/downloads.html