I'll accept your point about walking a dog, as it's often functional, i.e., just long enough to let them pee or poop, and the walker is often glued to their phone.
But why does strolling a baby or walking with a child necessarily "gain an aim"?
I'm asking because much of my walking is with my 2yo daughter, and I'd classify it as aimless walking. We'll just stroll around our neighborhood, taking whatever path strikes our fancy, and talk about the things we see: birds, squirrels, odd shaped leaves, puddles, people doing yard work – or just walk in silence and enjoy the fresh air. I guess I have the "aim" of getting a little physical activity and getting away from the distractions of technology, but if you dig deep enough, everything has a purpose – even if it's just to do something purposeless for a while.