We stayed in one last week in Seoul, only because hotels are prohibitively expensive. (We book last minute.)
On leaving, the host offered us a discount on future bookings if we left a 5-star review. This 'beg for a 5-star' practice is common in every Asian business. We got it from a Hilton in Vietnam. (It's probably global. Our recent experience happens to be in Asia.)
In fairness, hotel ratings are the same. My SOP now is to ignore all 5-star ratings. Simply don't read them. Instead, sort by lowest and that gives you the true measure of a place.
Ratings are totally broken.