At the time of interview, you don't know what the work environment and expectations will really be. We all hope that the reality doesn't deviate too much from the interview's image of it. But sometimes the reality is not as rosy as it was suggested. Or, perhaps things have changed over time.
Your advice then is to just quit, as if that is no big deal. That seems to ignore many realities of being without employment. Being without a paying job kind of sucks, and quitting can leave you out of work for long periods. "Just quit," is not great advice when it may quickly lead to homelessness, for example.
Rather than incur those realities, many find collective negotiation to be a useful tool to improve their situation.