It's sort of a truism that the more expensive software is to buy, the more expensive it is to own... (i.e. worse quality, less development on the part of the vendor, etc.)
If you're the only customer running OS/2-on-NT-using-Token-Ring-over-Carrier-Pidgeon, you're not going to have a good time when you find a bug or missing feature.
To name few examples - there's no decent alternative to Microsoft Office (free or otherwise), there're no decent open source alternatives to most CAD applications, to MATLAB (no, Octave doesn't count) & Simulink, LabVIEW, musical software, electronics design & manufacturing, etc. Essentially anywhere where the problem domain is nontrivial and the potential audience is limited.
I don't know what Microsoft Office has to do with this.
Microsoft Office is a good example of software that a) has a very broad audience, b) pretty much every computer user has seen, and c) somehow nobody can make a decent free replacement of.