Well, maintaining your current level of strength is far easier to do than maintaining continuous progress (especially at more advanced stages, which you have to do a lot of fuckery around programming/scheduling in order to realize any progress at all). You just can't do nothing, but the same goes for languages. If you don't use a language at all, your proficiency atrophies over time as well.
It's just not something people really think about. If you were to reach a level of strength you were happy with, you could just figure out a maintenance program and focus your physical energy on other pursuits, extreme sports, slacklining, bouldering, hiking, whatever.