Just curious, why would that be? Granted, I don't touch the flimsy trim tab on the rudder and don't bang any control to its stop either, but I always move ailerons, elevator and rudder and have a look at all visible elements. For the DA/DV 20 Katana, the POH even instructs you to check movement of the aileron linkage through a small plexiglass window on the underside of the wing, which would be impossible to do by moving the controls from the inside (unless of course one has such long arms that an airplane isn't really necessary for flying ).
As always, follow your POH. But the light aircraft I've flown all have "Don't push" written on the ailerons. I too check the bolts under the aileron that requires me to push it up. I remember my PPL books saying you shouldn't move them from the outside. The reason escapes me, maybe something to do with heavy handed pilots and the material of the surfaces, especially ailerons, seems like it wouldn't take much strength to damage.
Saying that, one of my instructors loved to move them all about so, as with many things in flying, everybody has their own ways. Just like how some instructors like me to get hands on with the prop and give it a good rub some instructors told me to treat it like its running.