several reasons. For some, because we think it might lead to useful results. For some, because we think the human pursuit of knowledge is worthwhile. For some, because we want to discover truths about logic and the universe. For some, because we are playing a status game (not just the mathematicians themselves but countries, universities, companies etc). For some, because we get personal fulfillment in understanding, and there being experts at something who can help others to understand.

For most, all of the above in various measure. To act as though one is the only thing thats important is wrong. The crisis is because the balance between these that existed is being shifted.