Intrusive linked lists as this is called removes unnecessary allocations and traversal (main reason why linked lists have such a horrible reputation), say a hypothetical example where you have a temporary listener object installed that listens to broadcasts on channel X and times out after 5 minutes.

Upon connecting the object is connected to the channel X linked list as well as some other list of objects that are killed at the timestamp 5 minutes in the future.

With an intrusive linked list the link-node resides within the object, the only thing needed when installing is linking it into the 2 lists (this is a few move-operations), an external linked list would _require 2 extra allocations_ for the linked-list nodes.

Broadcasting from X is almost the same since it's a simple traversal, albeit with double the cache pressure since the object and the linked-list node probably lives separately.

The real HORROR comes when disconnecting, if channel X has millions of listeners it could become a real bottleneck to traverse the linked list to find the link-node that connects the actual object since there could be tons of jumping around memory. An intrusive linked list would just disconnect itself if it's doubly-linked.

This is why hashsets/tables,vectors/arraylists,etc are often used in practice (because many "modern" OO languages never added good support for the machinery needed here) making linked lists look quite bad (there is other badness but using non-intrusive linked lists is almost always worse than using something else than a linked list altogether).