I used a kneeboard during my C-152/C-172 days. When I started multi training I decided to leave it in the seat pocket behind so it is in reach if needed, with the checklist attached to me at all times of course.
I agree about them restricting motion especially in most training aircraft.
If you're flying in shorts they make sense, though if you see a guy in pilot uniform with a kneeboard still strapped on walking around, it looks kinda funny.
Alex.