Presumably, that would be because the government of Israel has drawn them so as to define existential threats to the state, not simply as a matter of rhetorical posturing intended mostly for domestic political consumption.

CENTERFORSECURITYPOLICY: No-kidding red lines

And it's this dual - dual purpose, that has really plunged Lebanon into an existential crisis, because the state itself, the Lebanese state, must have a monopoly on the use of force.

NPR: Hezbollah's Evolution from Militants to Politicians