It brings foreign currency in, allows for the world economy to better function, keeps countries on their toes regarding upkeep of facilities, especially transport.
Certain ecological and economic criteria have to be met; I mean here, first the employment factor and secondly, the circumvention of externalities, i.e. it is possible to create a win-win-outcome by prudent economic policy.
Tourism promotes cultural awareness and also helps to preserve local culture and traditions. Money gained from tourism can be used to develop the infrastructure and services e.g. new roads and airports. It may help in creating employment for people of the country.
Flow of cash always add value which is beneficial for the country but if it has international tourism. It will be real benefit otherwise it is just transfer of money