Cloistered in their respective institutions, they often devote many years to subjects which garner little public interest, all the while living at subsistence levels and without real promise of monetary reward or peer recognition. Well, no doubt these and more count among the reasons. Some are noble, others are just plain baffling. But whatever brings one to graduate school, once there for a year or two, the culture can seem inescapable for those who want to keep their job options open. If you don't leave, the path of least resistance may end up going nowhere. .
Practical considerations are obviously one thing.
For example, you might consider what priority you place on job security or living location, and what the chances are of you getting what you want given the market and a reasonable assessment your abilities. There's a simple reason why. Philosophy markets are rarely hot even at the best of times. If you're dedicated, many of the above concerns simply fall away. On the other hand, if you're already thinking of leaving, your heart may be in the wrong place.