Laptops are more expensive than desktops, assuming you buy a business laptop with the normal enterprise features. They also take more abuse and need replaced a lot. However, companies reap the benefit in allow you to take work home with you (you work more), and in that you can be placed anywhere in an office and still productive.

I actually don't do any of my work locally, except for office stuff (mails, docs, ppt). All of my real work is on a server with big beefy hardware and enterprise level SLAs. I can reboot my laptop all day long for security patches and not interrupt my most important work. All of the laptops have SSDs (albeit with full disk encryption). No it's not a thin client, it's a full Windows install.