As a TB owner, I prefer to have the visits logged, better all than none. I have several TBs sitting in someone's backpack or sock drawer and despite the cachers' vow to take the TBs on cache travels, no visits have been logged. Sometimes a friendly reminder gets the TB moving again, sometimes not. I'm due to send out some secondary reminders, wish me luck. If they are getting visit logs, at least I have some assurance it has not gone missing.
So - in answer to the original question - No traveler logs occur automatically, if you decide to pick up a traveler visit to your heart's content and drop somewhere appropriate (CAVinoGal has a good method), or just leave in place and discover.