My In-Laws take about 2 trips a year, one to Vegas and one to a NACAR race. I've been booking their tickets for the past three years, and when I found out they didn't have ff# the first time I set them up I signed them up and just shook my head over all the miles lost over the years. To top it off, I was told by my father-in-law that it was a bad idea; now the airlines were sending him credit card offers and other junk mail.
Maybe he will see things differently when they both have 25K in miles after their trip next month to LAS. For them, just getting them to use a ff account was a small victory, it will still be a while until they understand the value of a mile!