The first reason that comes to mind is "control." Microsoft has control over not only the software they create, but the hardware manufacturers, other software vendors and even the customer data for those who used Microsoft products to create or manipulate it. The more one uses Microsoft products, the more they are locked into that software. And the more one gets locked in, the more difficult and costly it becomes to extricate oneself from their products.
Now of course, this argument can be made about products from companies other than Microsoft. A couple of decades ago proprietary UNIX Operating systems put users in the same situation. Luckily Linux and open source forced the vendors to give up some of the unfair control they had over customers and now we all benefit from faster rate of innovation, better compatibility and improved flexibility.
The problem with Microsoft is that between their operating systems and their office suite, break away is nearly impossible. One could say that it is not absolutely impossible since there are alternatives to Office on other Operating Systems such as OpenOffice and iWork on Linux and Mac OS X but then you have to worry that 99% of the people that will receive documents, spreadsheets and presentations will be on Windows desktops and may see weird formatting and a host of error messages. Nobody's trying to hide the fact that Microsoft's Office suite is offered on OS X. It is, but not too long ago, Internet Explorer used to be offered for the Mac too! Since that went away everybody started noticing all the incompatibilities on websites created with Microsoft tools when viewing them in Firefox or Safari. Is it a coincidence that sites build with MS products do not follow standards but everything somehow works with IE?
Choosing between Office on Windows and Office on OS X isn't really much of a choice at all. While no longer locked into the Windows OS, one is still locked into the Office suite. Those files are still locked in the Office format. But what about the other suites that can open Office documents?
The Office file formats aren't open specifications, so programs like OpenOffice and Abiword that usually open Office documents, occasionally have glitches. These glitches highlight the problem and give companies reasons to not rely on them and give in and become "customers for life".
These are just few reasons why open standards are preferable to Microsoft's closed architecture. You have the ability to create an application that is capable of reading or modifying a document created using OpenOffice on any operating system you choose to use. The source code is available and file format is open. Whether it is today, in ten or thirty years you will have ways of getting to your data other than paying a vendor whatever price they demand.
Another example of a Microsoft product that does not follow open standards and has proprietary undocumented components is Microsoft Exchange. Exchange has been around for a long time and customers have been forced through upgrades that did not offer fixes to the known problems but entitled them run a supported version with new features that are often not being used. Many companies were fine with the email and calendaring features they used in Exchange 2000 for example, and did not ask for anything other than the replacement of the proprietary database that Microsoft uses to store mailboxes. The JET database is a proprietary database that is underpowered and has many issues with the volume of emails and amount of digital content it is asked to store. It requires customers to use very expensive high end storage. Some of the common customer complaints are about backup and restore issues, archiving headaches, high maintenance and database corruptions, and yet every new release continues to use the same database and the same headaches.
Why is Microsoft not concerned with fixing this problem instead of introducing new features? Because they want to make the most money with the least investment and justify the premium they are charging for the new release. Looking at Exchange 2007 it is easy to see that almost everyone will be forced to pay almost 40% more than they would have paid a year ago for Exchange 2003. Another obvious reason why Microsoft does not feel pressured to replace the database and fix the host of problems it creates is that it is not likely that customers will drop their old data and Outlook to go elsewhere. It is hard to find a better example of vendor-lock. The only way a customer can find a safe alternative is to go to a platform that supports Outlook, Active Directory and Exchange until you have gradually migrated all your data and users. PostPath is a true alternative to Exchange. It is not only fully compatible with the above, it is also Linux based and uses the file system to store data. The advantage of saving data directly to the file system is that it scales, it is flexible, no special backup tool is required and you get access to a wide variety of commercial and open source products. PostPath gives you that option, whereas Microsoft forces you to choose from a much smaller, more expensive selection of products whose creators have paid them to earn the Microsoft seal of approval.
We have barely scratched the surface and we can see why companies shouldn't choose the Redmond Giant. Customers should look at alternatives that give them flexibility and freedom. After all, it is their data and they have the right to take it elsewhere.