Most of the places where I find myself on tour I am not especially worried about theft and many places I don't lock at all. My choice is between a light cable lock and no lock. A heavy chain or u lock aren't even an option I'd consider unless I changed my touring locale or habits. In the relatively rare times my tour takes me to places where I don't think the cable lock is sufficient, I just don't leave my bike unattended. I figure the risk of losing my bike to theft is real, but not all that great.

The times that I stay in larger towns with higher risks are likely to be the times I stay with a host or get a room.

It probably helps that I ride inexpensive bikes. I would be sad to lose the bike that carried me on all of my tours but the financial loss wouldn't be a huge hardship. $599 and I would have another one. Most of my gear is similarly inexpensive.