It comes as no shock to a longtime player that WoW's social culture is riddled with a number of real-life counterparts, and one of the more troublesome is something called the barrier to entry. In real life, this refers to the difficulty of becoming a qualified professional in a given field, and there are some jobs where the barrier to entry is very high indeed.
Take neurosurgery, for example. Ideally, you want to be completely sure of someone's aptitude for the job before you let them take a buzzsaw to your skull. Society relies on the grueling education and residency required to be a neurosurgeon to weed out anyone prone to use of the word, "Oops."
While there's nothing in WoW that comes close to the seriousness of getting a competent surgeon, most players would acknowledge that there are similarities between the RL and in-game version of the "barrier to entry." I'd argue that the comparison is strongest when you're discussing tanks. Tanks, and more importantly, beginner tanks who could potentially ease the tank shortage that causes lengthy queue times for DPS in the Dungeon Finder, have to hurdle a series of problems in the effort to become geared and experienced. Some of these problems are the result of deliberate design choices on Blizzard's part, but the larger share is the consequence of a playerbase that needs tanks but is (ironically) hostile to beginners.
Everyone wants an experienced professional. Nobody wants to be there for the learning process.
And if you're a beginner tank, there's a lot of crap in your way that Blizzard didn't put there.