If this is about specific movies, it is due to former actress delisting requests--required by Japanese law. Studios and platforms that legally show their work are never happy to submit movies to be delisted, but if they do not comply, they could face legal repercussion.
It still remains relatively uncommon in relation to the amount of content being created because most performers know very well what they are getting into. What only sometimes happens is some after retiring would like to fade into normalcy and thus initiate the process which still requires a decent amount of work on their end (it's not a "one click delist").
