Everyone should learn sign language so that they can communicate with deaf people. It can bring unexpected benefits. Here's an example:
My wife and I went to Ireland for our honeymoon. We hired a gypsy caravan, drawn by an independently- minded horse called Molly, and spent a few days traveling round the Dingle peninsula.
On the Thursday, we camped in Annascaul, and took a bus ride into Dingle. We took a boat trip round Dingle Bay and saw Fungi the dolphin, then we went into a pub for lunch.
In the pub I saw a deaf couple signing a conversation. Now I had worked at the East of Scotland Society for the Deaf, where I picked up a bit of sign language, so I signed "Hi there."
Their faces lit up. In no time I was telling them with my hands that we had come over from Scotland for our honeymoon, and that we had parked our caravan and horse in Annascaul, and we were enjoying our holiday in Ireland, and so on.
After our meal, we waved goodbye, and spent the rest of the day in Dingle, ending up in the cinema, watching Phenomenon starring John Travolta.
When we came out, we found we had missed the last bus back to Annascaul so we had to get a taxi. As we were waiting, who should appear, but this couple, and they lived in Annascaul! They invited us to share a taxi with them, and insisted on paying the fare!
Learn sign language. It comes in handy.