Humanitarian and Refugees organizations depend sometimes on volunteering work,is that based on lack of employees or it needs people who have passion?

both and its depend on the ground what it need from that work 

Qamar! There are many types of organization which work for this cause. some of them are self funded ( funded by their own members) and some are outsourced. 

The first type has limited sources and they keep their expenditures as minimum as possible and definitely need the volunteers, less employees and donations on humanitarian bases. The outsource and foreign funded organizations have sufficient funds to run their projects and have full flagged environments to run their daily routine matters ,  have more contacts both nationwide and internationally who raise funds for them.

So basic difference is Money and i will say " ITS ALL ABOUT MONEY"

Yes, because the work in the humanitarian field needs people to them with humanity motivated to do the work. this depends on the presence of people or society the situation materialist a good.But in societies that have their materialist situation worsening working for pay.In both cases, Humanitarian organizations do their part correctly.

sometimes the fund doesn't help the organization to hire people, so it depend on a voluntary work. However, lack of expert is also a reason of that.

I wish I could help you with my answer.

Yagout