Does trimming promote healthy hair?

As i watched this video, i came to the conclusion that many people believe trimming is necessary for healthy hair. I do agree that hair tends to look better and look healthier with a good trim, but does it actually make hair healthier to trim hair? What do you think? I will be on a no trim challenge on MyHairSistas starting september 3rd after using the moon calendar to trim my hair for thickness, and i will not trim again for at least 6 months. I want the healtiest hair possible, but after the 3rd not trims for a while, i hope i'm not doing harm, i usually trim after a relaxer, every 3 months