It's possible that the creators of Toy Story wanted to convey the idea of adventure and exploration for their little audience, hence the choice of Buzz Lightyear, who represents the vastness of the universe. And Woody, on the other hand, embodies loyalty, friendship, and all of them represent the importance of treasuring the things we hold dear. Tho, using characters like Mr. and Mrs. Potato might have made the movie feel more comedic or less relatable to a wider audience, possibly turning it into a different kind of film altogether.