I used a tent when I tour. The tent's rain fly provides some space under the fly but outside the tent (they call it a vestibule). I take my panniers off the bike and put them under the rain fly while I sleep. I use a Master lock and a thin cable to lock my bike at night. I always lock my bike to something as I've heard more than one story of a locked bike being stolen.
I rarely lock my bike when I go into a store or restaurant. I only lock it if I can't bring it inside with me or if I have to leave in a place that isn't in my sight at all times. My loaded bike weights 70 or so pounds and is a bit awkward to lift (let alone ride). It wouldn't be all that easy for someone to run up and grab it or ride it off. I may be being foolish but I always assume that I would react before the thief could get away.