Apart from delivering life lessons to kids, such recordings dedicated to relatives/friends could be used for a number of other reasons. Like recording important things you always wanted to say to those close to you, before you die.
Another aspect for which they could come in handy is recorded monologues about topics where you felt misunderstood by others. When it comes to relationships and communication with people, very often you get this feeling that there's one or a few parts of your personality that others don't quite get. Talking doesn't help, cause you feel that they don't get it anyway - your opinions, worldviews, personalities differ too greatly in that regard.
Similarly as with life lessons for kids, recording explanations about things/perspectives that are important to you and that make a big part of your identity, but are not understood or appreciated by others would bring a possibility that they will be understood/appreciated in the future, if not while you're alive, then likely after you die. It's often the case that you start understanding something a person was often saying to you and relate to that only after they are gone. Such recordings would let you listen to those things not only in your memory but in their own words and in much greater detail.
But those recordings might be useful in more situations than only after someone's death. For example, two friends haven't seen each other for a long time, they live in different countries now, etc. Because a lot of time has passed and they both went through many experiences, their personalities/worldviews changed and now they'd understand/relate to each other better in places they weren't able before. One friend has recorded a video for the other and uploaded it to the cloud 10 years ago, now the other friend decides to watch the video, he relates to everything expressed in the video and decides to reach out to the friend and meet him.