This is because it makes it possible to reduce the environmental impact of:
On average a camper holiday reduces per capita emissions by 33% compared to other types of tourism, and by as much as 200% compared to the plane+hotel formula*.
The gap may be even larger depending on the type of holiday.
For example*, per capita CO2 emissions generated by 4 people during a holiday lasting 35 days and travelling 2,500 km are approximately:

*Source: Öko-Institute. V.