The tradition of still life was often used as an opportunity for artists to create a realistic illusion of reality, as though the painting was an extension of the real world. The use of a "fake" frame allows us to consider our assumptions about what we see, our relationship to physical objects, and the role of the imagination in how we perceive the world.
A traditional 'vanitas' still life contained a symbolic message, with a burning candle or perishable fruit hinting at the transience of human life, while a skull could be a more overt "momento mori", a reminder of the inevitability off death. But a still life can imply a whole range of philosophical ideas and to comment on the values and beliefs of our culture and society.
figurative art: the philosophical still life
And remember, there's no such thing as a free lunch...