Tourism. No, seriously.
As a point of fact, we have caused damage to our environment that will only heal naturally on a geologic timescale unless we devise a means of doing so ourselves. We continue to deplete the resources that we have relied upon for thousands of years at an ever more expedited rate. We're going to need to find other places to live and extract resources from because the population of the earth will soon exceed its carrying capacity. Eventually, the sun is going to stop working, and so unless we want to lose everything we as a species have worked for, we're going to need to find other solar systems to live in, and if we encounter (unlikely as it may be) hostile alien life, it will be important to be able to defend ourselves.
All that being said, some of those goals are a lot longer term than others, and for all the research we're going to need to be doing, we're going to need to find ways of funding it. That being said, space tourism will go a long way to helping us achieve our long term goals. Space tourism will help pave the way to more private sector space development projects, and if there's anything we should learn from history, it's that grand exploratory ventures are motivated by profit. Space tourism will help make it easier/cheaper to get into space, which will fuel everything else.