Lantern helmet and Sunder enchantment

I’ve done a lot of research looking at the most optimal farming setup for my stage of the game, everybody is saying 3/4 melon armor and rancher boots is the best, but if you are above lvl 15 in farming lvl, why wouldn’t the Lantern Helmet be the most efficient? My only conclusion was that the farming fortune you get on the axe (and from the Sunder enchantment) doesn’t affect crops like: carrots, potatoes, wheat etc. But from what I have read, it does! So why would anyone not go with 2/4 melon and 2/4 pumpkin?