That isn't really the case at all though.
The problem is not with the tool(s) or the behavior they may facilitate. But one with the player base of a given game. In the case of World of Warcraft [many of these posts here are written with that POV in mind], the troublesome bits are likely with the player base that is one of the largest & broadest in all of gaming.
To be blunt: one is more likely to play along side cretins, children and jackasses in World of Warcraft than in other MMOs. It's just too big a game, appealing to an incredibly broad audience. Recount and similar tools are apart from that- totally.
Drop such tools in games like Rift, Everquest, Runes of Magic, Warhammer, et cetera- and there is markedly less toxicity due to the smaller, more niche audience those games attract by comparison to the more vulgar World of Warcraft.
The trick of selling a FFA-PvP MMO is creating the illusion among gankers that they are respectable fighters while protecting them from respectable fights, as their less skilled half would be massacred and quit instead of “HTFU” as they claim.
Not everyone knows how, or can be bothered, to parse combat logs, look it up later (and by "later" I mean by several hours if not days), and gloat to themselves or others about how they did 2.45% better than that other guy.
On the other hand, almost everyone knows how to download an executable file, run it, click "I accept" a few times (if Curse Client even requires that), and then click a button on a website to have all you need to gloat within a second of it happening. For that matter, installing it manually has never been very hard for anyone with a reasonable knowledge in Eningls Raednig 011.
Addons would have a far greater impact on the game than most people realize. Right now you can form a group of friends or even randoms, and do dungeons pretty smoothly. If we had addons we would be seeing that the DPS difference between players is enormous. A proper way of gearing and building would very fast emerge, and the profession/build imbalance would poke even the ultra-fan's eyes out. All that would have many social and general gameplay implications.
I hope they stay away from addons forever, maybe add a lot more UI options like being able to increase the god damn camera distance to at least twice what it is now.
But even beside parsers* Rift, Warhammer, AOC, ROM, TSW all have addon support of a similar manner. Even via Curse.
By no means would I say jerkface behavior is exclusive to World of Warcraft. But the number of people that play WoW is pretty significantly more than a lot of other MMOs. With a very high probability of running into dps chat spam dude due to the sheer volume and broadness of what is the most mass market MMO short of Toontown & Hello Kitty Adventure.
*I tend to call all combat logging tools parsers. Though admittedly that is incorrect on my part. Old habits and all that.
In all honesty, any time I play with someone who either links DPS results after each boss fight and goes "lol noob lock i did 900 dps more than u kick the scrub plz" or goes "link dps meter" every two minutes, I groan. Some part of me wants to say that if a DPS meter was supported that didn't allow for one-click announcements as well as only showed you your own performance would solve the problem... the lack of faith in the modern MMO playerbase advises me that it would merely drag it out with "did 4.3k dps that boss, say yours".
In the end, I still feel that addon support isn't something you should need in an MMO.
I'm all for addons. It's a shame GW2 didn't have it, maybe it could've made the game more enjoyable... who knows! I got my refund and all my friends too so we are happy but the extra addon boost maybe could've made the game alot more fun and kept us playing.
Play the game as it's meant to be played.
It's very easy to see that someone wiped you on Madness because they were not DPSing the small tentacles. Hell, you don't even have to switch views. Just hover over their name to see if they were attacking the right targets.
People who ignore damage to tunnel in on DPS are easy to spot. They're the ones with the highest healing taken or they're dead and way down on the damage list.
Healer not decursing? DPS not interrupting? DPS breaking CC when they shouldn't? It's all there.
I can see why some people don't like add-ons, but there's no need to spread misinformation about stuff like Recount. Recount is actually the best way to see who the stellar players are because you can see exactly what they're doing in a fight.
And Raiding guilds rely more on World of Logs than Recount. WoL gives you a even finer view of the fight down to which abilities each person was using.
I really have no issues with the current UI, so for me... meh. Addons have always been in a pain in the ass and what is the point of changing something that is working as intended?