Plates are generally only placed when the pipe or wire is within drywall-screw depth once you add drywall to the studs. They aren't infallible -- For example,

Plates are generally only placed when the pipe or wire is within drywall-screw depth once you add drywall to the studs. They aren't infallible -- For example, they don't protect against carpenters with nailguns patching sheathing on the outside who miss the stud entirely and hit a water pipe instead (you may wonder how I know this..) As for fiber cuts, one case I'm aware of involved a large diameter concrete drill/hole saw with a diamond-tipped blade. Not much you can do to armor against that.