The act itself is also shallow, flowers are meant more of a symbolic gift; I give my wife flowers maybe to express love but if I just gave some random person flowers on the street without any further explanation then I have simply given that person a dead plant. If the guy gave the lady something of actual value or that served a need, or even just made statement as to the meaning of the flowers it could have changed the dynamic. Further it is customary to ask someone (especially someone you do not know well) to accept a gift and to explain why the gift was given; there is a very good reason for this.