Linux already has greater market share in servers. IT pros using Linux in servers already are knowledgeable to facilitate the change. Also, cloud services work with any OS. Many businesses are switching to cloud based services.
Plus, budgets define these types of changes more than any other factor. The economy still hasn't fully recovered.
No, Linux has a greater market share of web servers. When it comes to servers in general, it's not even close. Windows still maintains a 70ish% market of all servers. What the IT pros know or don't know has nothing to do with whether a company makes the switch. It comes down to money, nothing more. And frankly, with all the internal systems that were built around IE, companies aren't going to be making the switch.
Let's not forgot how huge the Windows market share is on the desktop machines. There is absolutely zero reason to switch those over to Linux, especially with the internal systems built on IE (seeing a pattern here?). Not to mention the cost of training EVERYONE how to use Linux.
Many smaller businesses are switching to cloud-based. That won't happen with large anytime soon.
It would be nice to see more Linux machines in the business world, but it's just not going to happen.