Taxes like this are generally earmarked to fund the state tourism departments and to local government to pay for the increased need of public services. This way, Fire, Police and other emergency services of service to you are paid by you and not the local resident.
SD has a 1 1/2% tourism tax charged by businesses that recieve more than 50% of their income from tourism, on top of the statewide 4% sales tax. Then cities and counties may have an additional sales tax to fund their particular issues, the state parks have their own extra point or two to fund their own advertising budget. Thus in our state parks you may see rates vary a lot, from 4- 7.5%
Consequently, here you could see a minimum in a local park that primarily serves locals a 4% rate, to a mostly tourist park in a rural area required to charge an extra 1.5% so 5.5%,then another in a county or cities limits may have even more.
SD does not charge tax on stays of 30 days or more.
It could be that in other states they are establishing a flat rate so as to be an easier method to manage, then distribute to the agencies of need , like some states do with school districts?