Okay here's the thing: Let me add some details to dispell that "part-myth".
Salarymen do have long working hours & have to go along with those office drinking parties etc. But at the same time, they are treated more personally than an American enterprise employee would. Parents sick in old age? Many companies would give cash incentives to support. Buying a house? CEO might extend you a personal credit line or speak to his banker buddy to give you extremely favorable terms. Got married or had a child? Employers (not coworkers) would give you off-days & some cash/gifts to newborn. Did extremely well a financial quarter? You get a bonus "red letter" (typically a cheque or cash of good amount) or a paid short vacation. If you have passed your probation, Japanese companies will bend over their back to retain you (retrain, reassign under different manager etc.) rather than outright fire you (although thats slowly changing with the economy shrink)
Traditional Japanese companies treat their employees as half families. Managers tend to be more hands-on as a patriarch for the good or the bad. So while we concentrate mostly on the bad parts, we often overlook the good parts too.
I am in no way advocating their culture. Many things desperately need change. But if salaryman situation was so miserable, it would have changed a lot of things long time ago. No matter where we're born - freedom & comfort are valuable for everyone.
Managers becoming patriarchs (or even companies) can change the culture to then make individuals dependent on them. No patriarch, severely restricted options. That's a huge issue in Japan, and it's a huge issue outside Japan as well.
Giving people the stink eye for just mentioning leaving a company makes it easier for malicious companies (black companies in particular) to sink their teeth into naïve individuals. We see this problem in the West as well. We all know employees leave for pretty obvious reasons (and the reason they apply is obvious), but saying anything bad is the #1 sin of any job interview for very, very superficial reasons.
And neither of these are required to keep most of the solely good things.
A black company is basically a highly exploitative company. They will wring out employees for as much as possible, mostly within legal constraints, at the detriment of employees and the benefit of themselves. [0] probably explains it better.
Since changing jobs is seen as a huge risk and the culture among individuals is to remain loyal, it allows black companies to take advantage of naïve, mostly young individuals. You see similar things outside Japan, but less stigma on changing jobs makes it easier to get away from these situations.
>Which things?
E.g.: you don't need to be extremely judgmental of individuals ditching a job to still have the benefits of loyal employees being rewarded and having a family feeling within the company. Which would solve most of the problems with bad/malicious companies taking advantage of the situation.