Before The Burning Crusade, there simply wasn't any other way to get gear for your character but for it to drop past a certain point. Sometimes you could buy a BoE piece on the auction house - my first epic was a Brain Hacker my wife bought me on the AH. But in general, if you wanted a piece of gear, you farmed for it. You ran dungeons over and over again, hoping a piece would drop, and hoping you would win the roll - and if neither of those things happened, you just kept running. It was possible to run the same dungeon every day, over and over again, and never get that drop you wanted - one friend of mine never completed his dungeon set, even when he was working on raiding Ahn'Qiraj, because the shoulders simply would not drop.
But during BC the Badges of Justice were devised, and for the first time players had a way to get around the luck of the draw. Over the course of the expansion, new gear was placed on vendors, gear that could be purchased for Badges, and this meant that players kept running as much content that dropped those badges as possible. It's fair to say that the badge system kept Karazhan going as a desired raiding location - people would bring their geared mains, even, just to get the extra badges. When the Isle of Quel'Danas vendor opened, all of my friends and guildmates (who were raiding TK and SSC and moving up into Hyjal and the Black Temple) picked up gear from the IoQD vendor, because it was easily as good if not slightly better as the drops we already had. It filled weak spots (those pants or boots or belt that never dropped) or provided us with weapons absolutely as good as drops we hadn't even seen yet.
The badge system got ever more complex in Wrath, with each new raid tier also seeing the debut of a new type of badge and new gear that badge could be spent on. As a result, the two tiered point system (justice and valor points, honor and conquest points for PvP) was introduced in Cataclysm (technically, during the tail end of Wrath) to simplify everything. It worked, to a point. Now, in Mists of Pandaria, we've seen justice and valor points be superseded by the bonus roll mechanic, one that will be revamped in Warlords of Draenor. One could argue that the bonus roll system puts the emphasis back on whether or not an item drops as opposed to simply collecting points to buy an item - it removes the certainty of reaching enough points to make a purchase, as well.
The bonus roll mechanic may be getting smarter in Warlords, but at its heart, it departs from point or badge systems in that it returns emphasis to the random nature of loot. You can spend a bonus roll every week on a boss, and still never see that item you want or need - at one point I got the same pair of pants instead of the ring I needed four times. A bonus roll can net you the item you want, some other item, or nothing but gold - there is no certainty of getting anything you want with it. As a result, it serves to bring back the 'farm for it' mentality of the classic game while still giving you a second chance.
The problem with the badge/point systems ultimately is that they replaced random gearing to a degree. Furthermore, once you get the item you want (which you will get at a mathematically predictable time, i.e. 'as soon as you have enough badges/points') you'll stop wanting the points as well. Furthermore, before caps were put in place, the point system encourages binges. One runs the same dungeons over and over and over again, and never once even cares what drops - the only activity that the players care about is accumulating as many points as fast as possible. This led to dungeon blitzes at the end of Wrath of the Lich King, because literally the only thing anyone cared about was the badges. Even in Cataclysm and Mists with their caps, people still feel compelled to do just that, and cap valor.
Furthermore, the badge/point systems didn't do anything for players past a certain point. If you already had gear as good/better than what was on the vendors, even if you still needed upgrades, there were none to be had. Zip, zero, zilch. You weren't getting anything. Mists attempted to counter this by allowing gear to be upgrade via justice/valor points, but this just ended up as busywork that added a layer of gear inflation to an already inflated system. It's not like gear upgrading is optional. You'll do it, so it provides no gameplay at all, it's just a means to extend the use of points.
It feels to me as if we're missing other possible ways to work a compensation system into the game's loot mechanics. Bonus rolls have the disadvantage of being as random as the original system, while points and their ilk have their own host of problems. Other alternatives include tweaking the random chance so that, as a player farms a boss, the chance of him dropping an item increase. Perhaps this is what is meant by 'bonus rolls being smarter' in Warlords. Another potential way to make long droughts with bad luck on dice rolls less painful is to make crafting more rewarding - during BC, the blacksmithing weapons kept pace with raid drops. In addition, allowing dungeons and scenarios to provide loot that's competitive could help, as these can be more easily farmed than raids with weekly resets.
Whatever the ultimate system, however, it's been years since WoW was purely about the luck of the draw, and Warlords seems to be aiming to go more in that direction. We'll see how well it works out.