Working hard with long hours, based on my small opinion survey, is often prompted by identity and passion.
I've found many people who work long hours because their work is who they are, it is their identity. The alternatives, vacation, leisure time, recreation are less satisfying because they feel "less like myself" when they are not working.
In both cases, it seems to me that we have a New American Religion of work. The theology is amorphous, just as most American religion has an amorphous or non-existent theology. The daily practice of work, just as in Buddhism and Judaism, is the body of the religion.
The meaning and purpose of life become synonymous with work, so that work seems to become a fully-living concept. The decline of mainstream religions and the rise of highly personal religions seems to be a part of this development.