It is the question that stops more registrations than fitness does. The honest answer: the riding is the smaller half of this event. Everything people actually talk about afterwards — the towns, the tables, the music, the fire — happens when the bikes are put away, and a non-rider is there for all of it.
Breakfast together at camp, then the field rolls out and the day is theirs. Camp packs up around them and moves on to the next town.
Six Delta towns most people have never stopped in — museums, main streets, the river, and the kind of lunch counter you cannot find from an interstate.
They are at camp when you roll in. Dinner on the long tables, live music, the fire. This is the bit everybody remembers, and it is not a riding activity.
A non-rider registration is a real registration. It is not a plus-one who tags along — it is a place at the table, counted in the catering and the camp.
Non-riders get themselves between towns. There is no passenger shuttle following the route, so your non-rider needs a vehicle — which in practice means driving the day's distance on paved roads while you ride the gravel version of it.
Plenty of couples make this the good part: they get the town to themselves for a few hours before the field rolls in. It also means your car finishes the week in Arkansas City with you, rather than sitting in Jonesboro waiting for the shuttle.
Camp is a good week for kids — grass, tents, a fire, and several hundred people who will make a fuss of them.
Fifty non-rider places exist for the whole week, and they are added to your own registration rather than bought separately.