I don't think that's the reason. Valve is too small to really achieve anything with our user data, nor do they have any impetus to collect it. The Hardware Survey is technically optional, and my recommendations are so unbelievably poor that I can't seriously believe that feature ingests any individual user data.

I suspect it's more to do with the fact that without requiring a new Steam Ticket every once in a while, I could go and install much of my library on a friend's computer (or any number of friends!), rig the OS to deny Steam internet connectivity, and thereby allow them to play games with my licenses indefinitely and undetectably! The horror!