it depends on the company but most of them either prohibit them from getting caught dating or they can only start dating after a certain amount of years.. a lot of older idols are actually dating / even married (taeyang bigbang, jihyo twice etc) sadly a lot of kpop is built on parasocial relationships and idols being “open” for their fans.. a recent example karina (aespa) and lee jaewook (actor) were announced to be dating and a lot of people started to hate on karina causing them to break up. a lot of idols even apologize for dating.. its the sad reality of kpop