Knoware (pun intended, probably), my first Internet provider, back in 1993, had a 9600 baud connection to the Internet, shared by all his customers. When I phoned the guy (late, as he worked at night and slept during the day) to get a login, his first question was: do you have a Mac? There was no TCP/IP stack for Windows back then (Trumpet Winsock only came out in 1994, and was not a Microsoft product). He had heard of linux, said that it
probably would work, but I would be on my own.
Fast forward to 1995: Windows 95 still didn't have TCP/IP (that only came with service pack 1). MSN was clearly intended as a Windows Internet, to eclipse and make irrelevant the existing one, leaving Mac and linux outside in the cold.
Of course, the local pizza guy would have to pay to be on it. Win-win for Microsoft.