16x2 lcd with UnoR3 probs

he has the same problem as me, and i have noted the stern instructions that all the wires should be soldered to the LCD ,but having looked at the videos on youtube regarding connecting UNO to LCD ,none of them are soldered ,just having wires plugged in to a breadboard and they are all working just fine !
so how do you explain that ?

here is one thats the same as mine except no hello world display