The advantage of running a private tour is that the client has more control of the number of days, the sites visited, the itinerary, and the quality of hotels. So, when running a tour to raise money for a charity or non-profit, usually the tour can be custom-designed to fit the needs of the group.
Charitable organizations and non-profits usually have access and familiarity with large numbers of people who share at least one common interest. It makes it easier to recruit those interested in going on a trip. For instance, we had a group who was interested in classical music, so we designed an itinerary with a focus on classical music and the tour was a big hit, as well as raising funds for the organization. In another case, we had a group who was interested in hiking, mostly in the Northeast. But when we offered them a tour to Machu Picchu and Peru, it sold out almost immediately. The money raised from tour tour accounted for about 60% of the organization's operating budget for the next year.
Having contributors or members of an organization go on a small group tour builds loyalty. These people spend a week or so together, usually with officers from the non-profit/charitable organization and get to know them better.
Running tours is an easy way to raise funds for a non-profit in contrast to the traditional ways of asking for money.
For more information on The Traveling Professor's small group tours, see www.travelingprofessor.com