Thing is, when looked at in the context of a whole lifetime, motivations change, and often radically. I have friends who couldn't have imagined themselves running a half marathon or a marathon who eventually went on to do so. 10 years ago I couldn't have imagined myself doing an obstacle race, but then I started working out[1] and, hey presto, the impossible became possible. I still don't want to run a marathon, even though I know I could, because of the compromises it would force on me in terms of strength training, depending on what kind of time I'd like to finish in.

[1] I couldn't have imagined working out either but at 36 years old I found myself getting tired out walking upstairs, and having a torrid time with any kind of reasonably intense physical activity, and realised I needed to do something about it to avoid serious health problems later in life - and possibly not that much later.