Why would you want to use note cards rather than several pages of paper when giving a speech?

Because you not relying on, and reading from, a word-for-word text you are free to interact with your audience.

You are able to:

well seeing i am an artist and i actually did a self portrait; i will describe how i painted it.   i used acrylic on a stretch canvas about 4 feet wide by 6 feet tall. i painted myself smiling in a soft pink long dress, white tile floor sitting on a white couch with a table behind and a vase of gorgeous flowers.   i also had a round white hat with a soft pink ribbon through it laying on the floor and on the table behind me was a lit candle. i kept it simple but soft and romantic.