Whats the point about sippy cups?

I have a one year old who was being bottle fed all along. I bought a sippy cup today, and tried to make her drink from the sippy cup, which she did very easily!!! To me the sippy cup (NUBY make), is exactly like a feeding bottle, except its coloured and has a larger spout....so I am not sure how this helps in transitioning to a regular cup?? I see lots of literature on the web on 'transitioning' to a sippy cup etc. My bub didnt even react like it was a different to the bottle. Since it was way to easy + not very different from the feeding bottle, I want to know if I am doing something wrong, or am I missing some point?! Look forward to soime enlightenment! Thanks!