I think that was only true back in the 90s, when there were still other OSes to compete against Windows, like OS/2, Solaris and BeOS late in the decade. Once Microsoft effectively dominated the consumer PC market (2000s?), they turned around to threaten to never do business with OEMs that dared to bundle competitors' OS. They also did something similar in Japan, which destroyed NEC (who created the PC-88 and PC-98, the most popular 80s and early 90s computers there) dominance.