I'm going to call BS partly on this. Most of the business world is using basic productivity software, probably Microsoft Office, with some users needing access to an accounting package or CRM.
Thin clients aren't so much about up front cost as they are about reducing long term support costs. Using thin clients in an enterprise or small to medium business environment gives you a lot of benefits to the long term bottom line. From a security perspective, you cut the "attack surface" of your network very sharply - from dozens if not hundreds or even thousands of desktops that each need antivirus, security updates, administration, and security monitoring, down to a handful of servers that you can lock down pretty tightly. From a support perspective, you are no longer managing all those desktops, you are now managing a handful of servers. You have all the data for your organization where you can make sure backups are happening, and where you can keep tabs on what data is being stored and where it's stored, so you no longer have to worry about that file with a million customer social security numbers or credit card numbers sitting on someone's desktop, where you won't find out about it until after it walks out the door. Also, with a good setup, you ease the pain of patch days a fair bit, since you don't have to chase breakage across all those desktops, just across the app servers. You remove the expectation of user control because a thin client is clearly not a desktop (the "but I can do it at home, why can't I do it here" syndrome).
These are damn good reasons to go to thin clients on the desktop, even if the up front costs are the same or even slightly more, and they apply to most desktop users. Only "high-performance" application demands, like CAD, and software development need fat desktops. Now, on the laptop side of things, internet connections in the field aren't something you can count on, even with mobile broadband and wifi penetration, it's not always there, and it's not always good enough. so thin clients aren't going to make much headway there for a long, long time.