Why don't cereal companies put toys in the cereal boxes anymore?

That was my favorite part about getting a new box of cereal, picking out the one with the coolest toys. I remember when Toy Story first came out I got a Hamm (the pig) toy in my Cocoa Puffs. Even though I'm 18 I'd still get stoked to get a toy in my box of cereal and I'm kind of sad they don't do this anymore :(