It's visually more pleasing. 10:10: or it's symetrical opposite of 8:20.As they say rules are meant to be broken,I have seen watch image that is not either ( quater to 12'oclock)or may be just wrong?..haha.
Different product catagory require different lighting techniques like watch, jewelery like gold,diamonds/precious gems. You have to consider highly reflective surfaces and blown/overexposed highlights ( loss of details in bright areas) or shadow .Subject and backgrounds like white on white ( wedding dress) or black on black or white and black need exposure compensation.Sometimes light flair can be used creatively.For instance your watch photos have reflections that make the watch face partly disappear .Learn about what angles of incident and refractive light that does not appear in the image vs lens angle of view.Same goes for fish in a fishtank or highly reflective,shiny objects.
The point of focus is also important, like the leather bags, which is the main subject? Would it be better to have subject and prop/accesory ( camera/lens) in focus? I find the bag photos not sharp.Is it due to focussing or camera shake, is tripod used? You have to decide what is important to put emphasis on.If you want everything/element in focus, how to do it?
In general lines and diagonals are used to guide the viewer's eyes to the subject.Are you doing it effectively? The product is the star of the show understandable it must be viewed in it's entirety/complete/whole.Unless you are doing a layout or montage zooming in to show details.Lastly read some books on commercial photography and lighting.It will be a great help.