Why does PowerDVDSE have regional limitations?

The limit is done in accordance with the requirements specified by the major American film studios.

However, PowerDVD SE gives you the option of changing the regional setting up to five times (if your DVD-ROM is not regionally locked). When you get to the time of the 5th change, PowerDVD SE will automatically lock at the region-code setting you specified at the last time. After this time, you can only play back DVD titles from the same region code setting or non-CSS DVD titles for all regions.