Is a glass screen protector a good investment?

Episode 1394 (1:10:28)

Matthew from Panama City, FL
Invisible First Defense Liquid Glass Screen Protector

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.