You should find evidence of worms before de-worming them. Chickens can live with worms just fine. All wild-life have worms and they have been surviving that way for as long as they have existed. It is better that your chickens have a few worms than to routinely worm them. De-wormer is not good for your chickens. At all. You shouldn't de-worm them unless you have a worm problem. And a worm problem is different from just having worms.How do chickens get worms? Just from being outside in the world and eating whatever they can find?
Should we routinely worm them or should we find evidence of worms before subjecting the chickens to treatment?