why so many korean drama can’t be opened ?" can’t be open in you regional" WHY??
First of all this is a legal site, not a pirate site, so Viki does everything by legal licensing, and when you do that it means you have to obtain distribution rights from the producers, you make a deal with them. There are many global tv show platform , like Viki, who do the same, so it may be possible that in some cases others obtain exclusive online distribution rights for some regions, and Viki for others. If you cannot open it means Viki doesn’t have (yet) the license for that drama.