Why should the costume drama be filmed in Hengdian instead of the Forbidden City?

Hengdian is not a fake Forbidden City. Hengdian is a tourist attraction. What he is doing here is for tourists and filming! However, there are also some places where tourists are not allowed to come in, and only the crew is allowed to shoot! The Forbidden City belongs to a state-level protection unit, that is, tourists must strictly check, while Hengdian is different, all of them are modern handicrafts!