system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why weren’t James or Lily their own Secret-Keepers?

In *DH*, we find out that you can be your own Secret-Keeper, since that’s what Bill did.
gpt
You would actually have to leave the safety of your home to invite someone. Having someone you trust on the outside makes communication with the rest of the world much easier. Bill never was as hunted as the Potters were so it's wasn't that dangerous for him to leave his home.

Of course you could do it like the Order did with Dumbledore writing the adress down but that's pretty risky as well.