You don’t have to.. we never did. It’s a personal preference I guess. I noticed a recipe with how to pictures when I was searching yesterday that did do that here:
http://www.pickyourown.org/tomatoes_sun_dried.htm
that’s an awesome website- thanks. I did a trial run and they were fantastic! like tomato candy. I did what the first instruction said not to and used cherry tomatoes since I am overloaded with those. I harvest probably 2-4 cups a day from all volunteer plants. I cut them in half, squeezed out most of the seeds, and in 5 hours, they were dried and delicious!