What desktop PC? Running what? I do have a desktop PC and I do do business with Word documents. But on my latest machine I have yet to install Office (though I have two legal copies) because Google Docs works just fine.
Sarcasm aside, a lot of people still use Office. Far more than use Google Docs. Even businesses that are using Google Apps for e-mail still use Office for their documents. Being able to edit documents with 100% reliability on a tablet could be a big deal when it comes to corporate tablet purchases, for a start.
"Microsoft’s average revenue from its Office suite licenses sold to enterprise and retail customers has been declining due to competition from cloud-based app providers like Google, Amazon and Salesforce.com, and also due to increasing lower priced products sales in emerging markets."
There are still a ton of companies out there that use office. Creating a Windows Tablet could well cause sales of Office to increase.