Because a tourist is neither commanding, piloting, nor a crew member of a spacecraft, but will likely be performing tasks outside Earth atmosphere.
As it says, the cosmonaut's definition is personnel that perform tasks outside the Earth's atmosphere. While the astronaut is tasked with certain high level things compared to space tourists, such as flying the spacecraft.
my task is to travel to space not commanding or piloting nither servicing as crew
I think Astronaut sounds like it should be reserved for the crew, or the piloting individuals of the craft.
If Astronaut is defined as "tasked with commanding", and Cosmonaut is "personnel that perform tasks", It implies that astronaut may be the commanding party of a mission.
Tourists are simply coming along for the ride.
because in the etymology of the word cosmonauts it means "space sailor" that's why space tourists best describes cosmonaut.
