When someone passes away, their loved ones have to deal with many issues. While surely not the highest on the list of priorities, taking care of the Facebook account can still help to deal with the loss. Having the Facebook account showing up in Messenger and on Facebook itself can cause additional stress.
If the deceased was a prolific Facebook user, and the account is full of photographs and other memories that should be preserved. Memorializing a Facebook account is one way to preserve this memory.
Another reason is security: You need to make sure your loved one's Facebook account is memorialized sooner rather than later because after their death the account might become a target of people with malicious intentions. Memorializing the account protects it from further logins.
This is what happens when Facebook memorializes an account:
The account is locked down. This prevents any attempts to log in. Ensuring the account is protected. Understand better what you need to do to protect your Facebook account.
After memorializing, no changes are permitted to the account. At this point, no friends can be added or removed. No photos, posts, etc. can be edited or deleted.
Posts on the account's timeline are possible, if the privacy settings allow for it. This way friends and family can post tribute messages. This setting should be considered before memorializing the account.
Similarly, depending on the account's privacy settings, the visibility remains the same. Anyone who could see the account's Posts, Photos, Comments, and Likes will still be able to see them after the account has been memorialized.
The "People You May Know"-section or birthday reminders will not include any memorialized accounts.
Facebook makes it easy to memorialize the account of your loved one. You will need to request the change by completing a "Memorialization Request". To complete the process, you will need proof of death.