We use them when we go. We have ones with subchannels as well. They make it easier for when we have large groups and we want to split up for a little bit. I'm also one that doesn't like roller coasters or any kind of scary ride. So last year, when there were rides I didn't want to go on, my boyfriend would take one and go on the rides with his daughter and I would go look in the shops. They would let me know when they were leaving the rides and we would meet up.
We also drive down to Florida from Virginia every year, usually in several different cars, so it makes it easier to communicate between cars.