From the Working with guys http://www.theyeshivaworld.com/coffeeroom/topic/working-with-guys
as well as other threads, you can see why someone would specificly NOT look to hire frum individuals.
I know a frum business woman who tried not to hire frum women. From her experience, they were just not reliable (whether taking off for a siddur play or a week before pesach to clean is justified or not, those were the facts).