I think doing a Trans America as a first and only tour is pretty common. A fairly large percentage of the folks we met on the TA were doing it as what they expected to be a one time thing. Many were doing it as an after college fling. There were also some doing it as an after retirement fling. A good portion of the folks I met on the TA were much more focused on doing a TA for the sake of doing a TA more so than for becoming bike tourists.

I think that may be kind of unique to that particular route though as I have not observed the same on other routes. The route started out as Bikecentennial, where lots of folks did it to see the US and celebrate the bicentennial year much more so than to become bike tourists. I think that kind of lives on today.

I do suspect that some of the one time tourists I met on the TA will come back to touring at some point later in their lives.

BTW, since you mentioned Stucke, I will say that for me being on the road full time has absolutely no appeal at all. I am generally very ready to go home to my family and my dog at the end of my tours. On the other hand, for me, really short tours have all the appeal of camping in the back yard. I think that if I had started out doing overnight or weekend tours I would have lost interest quickly. Everyone is different.