My father was accused of being "anti-Microsoft" sometime in the early 90s, because he kept pushing for cheaper alternatives. He was writing Windows books at the time, so he ended up bringing in a book to show them.
A lot of this purchasing is purely "cover your ass" thinking. Going with IBM, Microsoft or Oracle won't get you fired.
I don't have a lot of love for MS today, but you'd be hard-pressed to compare the MS of today to the MS of the early 90s. Find some developer magazines from that time and check out their ads - they were still scrambling to grab market share in areas other than DOS/Windows for client PCs, and had a lot of competition in the form of Borland, Lotus, Novell, and Oracle, as well as smaller fish like Watcom, Gupta Technologies, Fox Software, etc.
A lot of this purchasing is purely "cover your ass" thinking. Going with IBM, Microsoft or Oracle won't get you fired.