I have noticed that for most pilots, newer pilots in particular, the technique and observation points for a walkaround check have been trained by an instructor, rather than a maintainer. The result can be looking for lesser importance detail items, while overlooking big things.
While training for my helicopter license, I was trained the walkaround. On my own, I added a few checks. The result was I found that the tailboom (SW300) was loose. My instructor was shocked at this condition, and that I had found it, the maintained seemed a little embarrassed that it had not been noticed sooner.
Shake and observe the big things too!