The most mature effect of developing a culture-oriented society is the ability to spread your culture to other nations in the world. When you have prepared the basis of a powerful and influential culture, it becomes to the other's benefit to partake of it. Implementing a Cultural Exchange program is the practical way to do that, and it has an immediate effect on your nation's cultural influence.
This level 3 Policy is one of the most directed and powerful in the whole game - directed, because it only serves Tourism; powerful, because a 15% increase of these three bonuses provides a potential 45% increase in total touristic output, as soon as you adopt the Policy! This is a great boon for any player pursuing cultural victory.
Of course, all is not roses. Note that this is a potential increase - you still need to activate the relevant bonus in order to use the increase. In other words, if you don't have an Open Borders treaty with a nation, you can't enjoy a +15% influence on them, can you. So, you still need to work for your bonuses, but when you achieve them, they will be significantly higher than those of other players, thus allowing you to progress faster towards influencing other nations.
Although there were unofficial cultural exchanges – the visiting of students, artists, athletes and others on a quid-pro-quo basis between nations – as early as the beginning of the Industrial Age, such programs became formalized by opposing governments during the Cold War, when the USA and USSR sought to simultaneously display the superiority of their respective cultures worldwide and enhance mutual understanding of their respective value systems. These formal programs eased the restrictions on travel and performance by select groups in "enemy territory," a process that several historians have declared to be a "cultural Trojan Horse" because such programs eventually "eroded" Soviet rule.