1- Microsoft gains nothing in the deal
The simplest reason Microsoft won't buy Nokia is this: Microsoft gets nothing out of the deal. Microsoft already has what it wants out of Nokia -- that the world's largest phone manufacturer settle on Windows Phone 7 as its smartphone operating system. Why spend billions for something you've already got?
2- Microsoft would be buying businesses it has no interest in
Nokia makes a lot more than just smartphones, notably inexpensive, low-end phones. That's a business Microsoft has absolutely no interest in, and would gain nothing from owning. Why buy something that would just be a drag on your business and offer no strategic value?
3- Combining corporate cultures could be nightmarish
Whenever one company buys another, there's inevitable conflict as the two firms try to merge corporate cultures and business practices. Microsoft is at a crossroads right now, facing multiple challenges, most notably in mobile, Internet search, and the cloud. The last thing it needs is that type of distraction.
Now here is 3 reasons Microsoft may take the plunge and buy Nokia:
1- Patents, patents, patents
As Microsoft knows better than any company, patents have become powerful assets. Microsoft has sued or threatened to sue makers of Android cell phones based on what it claims are patent infringements, and has gotten hundreds of millions of dollars in returns. Adding Nokia's considerable number of patents on mobile phones would make Microsoft even more formidable.
2- Nokia could be bought relatively cheaply
Paulo Santos of the Seeking Alpha investing Web site claims that because of Nokia's market woes, Microsoft could buy Nokia relatively cheaply. He figures that even paying a 50% premium, Microsoft would pay $21 billion. Given that Nokia is sitting on what Santos says is $6.6 billion in cash, and that Microsoft would likely sell off Nokia's telecom equipment division, that's not an outrageous amount for what Microsoft would get. Consider that Google is buying the smaller Motorola Mobility for $12.5 billion, Microsoft could almost be considered as getting a good deal.
3- Microsoft needs to follow Apple's and Google's lead
With Google buying Motorola, Microsoft will be the only major maker of smartphone operating systems that doesn't also manufacture hardware. Apple, RIM, and now Google all make phone hardware as well as smartphone operating systems. As Apple has long shown, if you make the hardware and the software, you can design the best possible user experience. So in buying Nokia, Microsoft would be more likely to do the same.