Yes it's nice being able to save without a card. however there is a positive side to having a memory card.
1. You're Xbox takes a tumble down the stairs and brakes. Even if you get a new xbox you can't continue your saved data.
2. You're going to a friends house. You want to take your saved game over and play around with it. Fit a little card in your pocket instead of draging a big bulky consle over.
So as you can see there are advantages and dis advantages.