I've been ranting up and down the boards for literally years now talking about this very fact, that even in 2017 "adc lul" era, they STILL have not needed LW for two years, and growing on a third, ever since the end of Season 5.
If you invest in damage, you get that damage and its gold's worth no matter what, unless you're CCed. You invest in defense, and your opponent's investment in offense already negates everything you're building and then some (come late game/3+ items) before they even need to remove fucking half you resists with LW, or (god forbid) before they need LDR's up to 20% more physical damage from all sources, including all of their spells Oh, and yes, that's scaling multiplicatively as a 1.2 modifier-- this is massive, with 50% crit chance, an IE and the attack speed from a single zeal item, (so if you build LDR as early as third item not counting boots, and are at least level 9 and not Jhin) LDR's passive adds an extra .4 DPS per point of AD, taking an ADC with zealitem + IE from 1.875 DPS per point of AD to 2.275 DPS per AD, before factoring in 35% bonus armor penetration, and the increased DPS from similarly scaling up all other source of physical damage (including on-hits from items like runaan's and BotRK).
The fact that they have THE TANK BUSTER ITEM to such an extent that if an ADC buys an LDR, a tank's health and armor items will be worth more to them sold back to the shop at the 70% rate, and then replaced with offensives item to attempt to one-shot the ADC first-- and yet no one EVER builds it should tell you just how worthless armor actually is, and how fucking overloaded and gamewarping ADCs multiplicative scalings are.
It is worth noting that pretty much only ADCs, Yasuo and GP can abuse this system, and huh. . . who have been the most complained about or busted champs recently?
GP been topping winrates and pickrates at high Elos ever since he got systemically buffed to scale into his crit build quicker with Klepto? Huh, who could have guessed it? Pros and streams bitching about the game and threatening to, or actually leaving League to stream other games because "Skill doesn't matter anymore," and "The botlane always decides the game" and complaining about ADCs scaling past their entire team's ability to deal with them.
Hmm. . . maybe getting upwards of 5.0 damage per second per singular point of AD (which they also get in abundance as well, even on their "defensive" items) come lategame, while other classes are constrained to linear scaling for defense (but, even less than that with regards to the bonus armor pen from LW, actually makes an asymptote, or at least a kink where base armor ends and bonus armor begins) or quadratic scaling for spells (both magical and physical) and for on-hit effects might be just a tad broken.
Imagine a mage with an AP ratio on a manaless point and click ability that auto fires itself again in as little as .4 seconds, that starts at a 1.0 AP ratio, only for it to increase to over 6.0 and turn into AoE, and be delivered at 700+ range lategame? Would be bullshit and game breaking. Yet Jinx with her Q and Twitch with his ult, and both of them having full builds, they'll do just that and more, 'cept with AD o' course. See, in addition to all that, if they have a Runaan's as one of their items, the AoE effects they trigger can overlap, and you have what MMORPGS and ARPGS call "shotgunning," which has such ludicrous damage scaling if it happens, whole teams die virtually instantly in the span of 1-3 auto attacks.
Makes you wonder why we're in League of Hypercarries, huh?