It seems to me that many people find it hard to believe that one can commit to a life of helping fellow human beings for absolutely no pay in return.
I remember watching a Japanese game show on TV with my 22-year-old nice. Participants are given very difficult tasks to complete - like hand-walking along a path with numerous hurdles. Halfway through, my nice asked me what prizes the guys were competing for. I told her I didn't think there was any - I had never seen anyone getting anything.
She was shocked and responded: "You mean they do all this for nothing!?"
I asked her: "can't you do something for the fun of it?"
"No way!" was her answer.
Nothing is real unless it can be named; nothing has value unless it can be sold; money is worthless unless you spend it.