Booster services have appeared in games… a long time ago. In the modern world, boosting is an integral part of the game. The Blizzard Entertainment User Agreement regulates the activity of boosters in some way. The fact is that in the game, first, you cannot sell services for real money and a ban may come for this, and, second, you cannot transfer your account to third parties. Considering that some types of boosting require the transfer of an account, this complicates the situation, although not much.
Boosting is popular in World of Warcraft largely because it is an MMORPG game that has been around for many years, and probably will be around for as long. Accordingly, there are a lot of activities in it, which, with all your desire, you will not have time to work out.
And there is also much collectible content, such as achievements, mounts, pets, titles. And some content disappears altogether after some time and players want to have time to get some evidence of their heroism, even if it was not there at all.
Not all Blizzard games are popular with boosters and buyers. In the first place, of course, the Second World War. Players buy everything from gear to levelling, from gold to ratings. Hearthstone is in second place, where accounts and ratings are sold. Next, Overwatch broke into the top three, where the same accounts, ratings, and skins are sold.
Other Blizzard games are not at all popular with boosters, because there is nothing to boost. There are, of course, a few sellers and a few buyers, but this is a drop in the bucket.
As for the attitude of developers towards boosting… Of course they are against it. They are against when money bypasses their pockets and directly falls into the hands of boosters. Still, the token system allows players to buy it for another currency (almost three times more expensive than on various third-party sites), sell it for gold and spend this gold on buying services from boosters.
Moreover, in one of his interviews, the WoW director even mentioned that they were thinking about introducing a special interface for boosting so that sellers would not download chats. And he openly stated that he was not against selling services for gold, because it does not harm the game. Like, imagine yourself as a traveller in some world. You need to get an artifact, but you’re not strong enough. Still, there is a hard coin. You can hire mercenaries, right? So why is WoW boosting worse?