"The creative act is not performed by the artist alone. The spectator brings the work into contact with the external world by deciphering and interpreting its inner qualification and thus adds his contribution to the creative act."
Taken from a recording of Marcel Duchamp made in 1957 titled 'The Creative Act'
The spectators interpretation of the work is both enabled but also clouded by cultural references built up over their lifetime. That's why, with its dominance in the international bank of references, this is recognised as being a sign for Coca-cola
and in London this is recognised as being a sign for Costcutter. So while it's true and important that we all interpret things differently we also all interpret things very similarly.