The first reason the private transfer is a safer option is fewer people are around. Since fewer people are around, it is easier to avoid being lost, but also easier to find luggage and other items. Without this type of feature, people may end up losing some of their luggage or even worse getting lost when they are trying to find their connecting flight.
A second reason the private transfer is safer is the airports are typically not hounded by the press or other individuals who are looking for any little bit of news. Since people are not present looking for any type of news, it allows people to get to enjoy the comfort of the airport. Since people get to enjoy the comfort of the airport, they are more likely to have a better trip and get to learn more about the area, rather than feeling like they have to rush to another area.
As many people have found out moving from one airplane to another in a major terminal is quite the rush and can lead to them missing the flights if they are not careful and safe. However, the smaller private airports often allow people to have a safe transfer and relax when they are getting ready to head to the new plane. The problem is many people do not know about the safety that is present in the private transfers and still opt for the major airport transfers and the crowds.