The trend is that everything important goes to the cloud, where people add and access data from all their devices including PCs, tablets and phones. What's running on your desktop is not really important, when the cloud providers have access to it because it their servers, not yours and governments just happen to either scoop up the traffic or have special access to it.

What's more private, a Word document sitting only on your drive on Windows, or the same information in a Google Doc that you uploaded from a hardened Linux machine over TOR? In that sense, what the desktop runs is becoming less important. In the first case, your file is unlikely to be accessed unless you're a person of significant interest to a government and takes some effort. In the second case, as it was revealed, it's almost routinely scanned or can be accessed with the click of a few buttons. A super secure USB booted secured PC running OpenBSD is not going to help you once the document reaches the internet/cloud.