agree with Forcus, but this comment from an employer about says it all
The truth of the matter is that you are not going to be given the "chance" or the raise or the promotion unless you are always working hard and prove to your employer that the job takes priority over family, lifestyle, and your personal life from 9-5 and you are dedicated to the success of the employer and the client.
Fortunately, I don't need the money so badly that I'm willing to give up family, lifestyle, and personal life for a 9-5.
I was about to say that the above is not true. However, it might be true. I think one does have to be dedicated to success. What "success" is and how that gets achieved (and how long it takes to achieve it) is really the factor as to whether you get to prioritize family or not. Also, it's more likely you will *get* to prioritize family if you do, indeed, prioritize family. Look at Sheryl Sandberg's "alarming" revelation that she leaves the office at 5:30. She was scared to say it, but she did. She even talks about trying to get out of the office with no one seeing her.
At a certain level and in a certain type of job, one can gain flexibility to prioritize family during regular hours. I work irregular hours at times. In return, my employer (my boss, really) is flexible with me. However, I have demonstrated my dedication and achieved outstanding results, which naturally makes the place more likely to be flexible with me. Also, my boss wants flexibility. =-) And so, I think, does his boss.
Employers know it's expensive to replace good talent. If you are good talent--and you are not working for crazy people--then it's more likely that they will be flexible. I think we, as a culture, are slowly moving toward blending work and non-work lives. I hope that official 9-5 work becomes passe.
On a related topic, I work in a place with a lot of people who work from home, other states, etc. The company loves it that they do not have to pay rent for places for people to sit. In the end, everyone gets more flexibility and saves money.