The simple fact is that it's much easier to just rebuild an infected or compromised laptop than re-tool your entire company to use Linux. Far, far cheaper, as you will already have someone in-house building new laptops anyway; the process is no different, just a few more man-hours.
Any sensibly-run company will use a mixture of technologies; Unix is strong on scalability and security, Windows for ease-of-implementation, off-the-shelf solutions and rapid development, mostly due to the widespread availability of cheap skills, and an out-of-the-box extensible directory service that makes user management a lot easier. Linux for web services, appliances and VM hosting.
There is no black and white solution to questions of this kind, but the argument against Linux is the same for any OS out of its comfort zone: cost.
UNIX is hot. It's more than hot. It's steaming. It's quicksilver lightning with a laserbeam kicker. -- Michael Jay Tucker