I think it's more like it's the low-friction way to go. Most enterprises do not have as their core mission the production of documents. Dealing with documents, spreadsheets, presentations, etc. is a requirement but it's not their core business mission. Spending time identifying, installing, and managing a hodgepodge of other software to do what Office does has no return on investment. Specifying the standard complement of software for an employee PC becomes a 2-second exercise: Office. Done. Now I can think about something that might add value to what we do as a business.