Too much depends on the quality of work expected from their cast and crew to permit a roll in the hay to jeopardize their professional futures. But these people are few and far between, and do not reflect the reality of getting a job in the film industry. When they are on a project, they don't see their family until the project is done. Most importantly, they love every minute of it. The moment you are hired on to a set, you are a professional.
Professionals are people who can produce high-quality work, regardless of other considerations.
It never enters his head that he is just there for the ride, or that it's enough just to be on the set and experience the so-called glamour of the film world. A professional knows the rules of the game as a matter of course and will seek to achieve the highest quality in his or her work. That means consistently striving to be the best at whatever you do and convincing your employer that it is not only worth it to keep you on this job but also to hire you for the next one. You can't be a light bulb. A person can be in good spirits most of the time, and occasionally have an off day.