Mark noticed his daughter's phone has a crack in the screen, even though she has a screen protector. Leo says that the very nature of glass, no matter what kind it is, is that it can crack if it gets hit just right. All a screen protector really does is protect from scratches.
Matthew got a new phone and they put a liquid glass screen protector on it. Leo has his doubts that a layer will really protect it. He's tried Liquipel on his iPhone once and it didn't protect it from submersion. It could be there for scratch protection, but then if that extra layer scratches, he'll be left with the same issue.
The spray is Silicon Oxide, which the chatroom says is quartz. So it may be fine. But why wouldn't Apple, Samsung, and others do it if it worked? Only time will tell.
Ron just bought a Droid Turbo. Should he buy a screen protector for it? Leo says no. Gorilla Glass is at the point now that it's really good against scratching. And that's really all a screen protector will protect against. Nothing will protect his screen from breaking if he drops the phone. But a case is a good idea.