Most friends I've had that pick numbers and play the lotto do it to break up some of the monotony of life. They're at the stage of life where they realize all their dreams as a kid aren't going to come true, they aren't going to strike it rich, and they'll be doing good to retire at 65. It's just a way to keep the dream alive.
If you try scratch-offs, make sure to check your state lottery website. They provide up to date records of how many have been sold and what prizes have been claimed. Don't lower the already small odds you have by playing a game where the big prizes are already taken.