Point remains, there is no one solution ... it depends on the peace of mind/fear factor of the owner, the location and duration where the bike will be left, and the value of the bike.
The only way to remove all risk of bike theft is to not own a bike.
On the other hand, the majority of cyclists never have their bikes stolen.
I cannot see why anyone would leave a bike where they thought it would be stolen ... if it was me and I had not choice, I would ride a bike On Those Occasions that was too cheap for anyone but a joyrider to steal, and use just enough lock and chain to defeat a joyrider/thief.
I don't have a lock on my CF "superbike" (it isn't "super" but it is way more super than me.) But I simply won't leave it. If nature calls, I will find somewhere I can answer with my bike in sight. I bring bottles and bars, tools and tubes so I don't need to stop at a store.
As others ask ... why buy a bike lighter than all the rest I own, only to equal out the weight with a hefty locking system. Seems I'd be just as well off with one of my other bikes then.