IF I HAD A DOLLAR FOR EVERYTIME....

As odd as it may sound, modeling is a job.  The word that should stick out there is "job".  When you look at an ad for a cosmetic line the concept was created by people who have jobs in advertising.  The client called the advertiser, met and discussed working together within their workday...which was most likely between 8am and 6pm.

Once hired the advertisers make calls to photographers, set up times to go over concepts, etc...once again during their workday.  In turn one of several people (photographer, casting director, ad agency) contact model agencies to hire models all during regular business hours to hire models.

Modeling agencies reach out to models, typically during business hours to hire models to hear...

"Unfortunately she has to work till 5.  She was trying to leave early.   Are these castings usually during the weekdays?  Thank you for the opportunity maybe next time it'll work out with our schedules. 

Or 

"Thank you so much for thinking of us but we could not do that.  Unfortunately it is tough for us since we both work..."

It's like the train comes to a screeching halt....Granted this is not all models, experienced models obviously have a clue but this does lead me to ask?  

If you have a job, why seek out another without understanding what it entails?  

Or

If you were looking for a part-time position at a store, wouldn't you ask what your hours would be so they would not conflict with your work schedule?  

Or 

Would you accept the job and when they call you to report to work on Monday you answer with, "does the work only happen Monday-Friday 9-5?"

The exception to the 9-5 rule is Fashion shows and of course fashion week and depending on where you are located (travel, etc) could take time outside of the 9-5.  In a primary market like NYC, Paris, Milan, etc and you would most likely be booked all day and well into the wee morning hours.