In low Elo (imo, gold down) taking Thunderlords isn't necessary. The idea behind Thunderlords being so fantastic is that it lets you dominate in lane and in theory translate that lane dominance into a win during the mid game because of the lead you acquire.
The reason this is almost irrelevant in lower elo is because people don't know how to properly close out a game and the potential for come back wins is always prevalent. In the mid and especially late game, Thunderlords is outclassed by at the very least Warlords Bloodlust on high crit champs (pretty much all ADCs atm, as well as Yas and Tryn) and potentially even Fervor of Battle (though im less sure on this one). Deathfire Touch is pretty much always better than Thunderlords on DoT based champions such as Malz/Brand as well.
The current obsession with Thunderlords is because that's what high elo people think/do, and as a result low elo people are following suit without realizing that just because something works in high elo doesn't mean its going to be as great in low elo.
Personally, ive tried using Thunderlords on ADCs (Lucian) and was very unimpressed with it. I find I get far better results with Warlords Bloodlust due to its incredible survivability late game.