Are they intimidated by the technology of prebooking FPs, the inconvenience, the thought of a schedule...???
My sister (of about 60yo) is using FPs for the first time this April. She was always intimidated by the thought of a schedule and the technology of using an "app". Now she realizes she is going to be "somewhere" in the park at "sometime". And, not only is it free to use, but I had to convince her it is also free to NOT use. She felt if she booked a FP, she would feel obligated to be there at that time. I had to show her how to cancel, modify or just "Let it Go". So she is now experimenting with the FP system.
Your friends may just need you to take them by the hand and show them how to do it.