Well, the alternative is to be an originalist, trying to determine what a bunch of dead white guys in the 16th century -meant- when they wrote it, which is big in a number of conservative circles, and amongst a number of conservative justices.

Personally, I find that an unhelpful approach because the world, and yes, society, change. But it -can- be a helpful guiding star. Those who don't learn from history, etc; well, we have this document that was very intentionally trying to protect against a variety of evils that had been directly observed. Reintepreting it to today gives us value, in that it's a warning against behaviors that are detrimental to society. What exactly is the extent of freedom of speech? The document won't tell you that, or what a good extent of it should be, but it -does- tell you that -it's important-. The countries with the most restrictive speech, the ones where the wrong words routinely get you thrown in jail, where there is little to no free press...there is no document the government is predicated on saying that freedom of speech is important. Etc.