What games are we talking about?
candy crush saga?
farmville?
robot unicorn attack?
solitaire?
Sure, you don't need a dedicated graphic card for internet, office work, most of the casual time killers and old games /since the integrated GPU beats many old dedicated GPUs/.
But once you want to play some newer games at reasonable settings and FPS you will need a dedicated GPU.
Also, there is the question - what GPU? Sometimes the GPU can be weaker than the integrated one...