They solve the problem of not having to copy pasta your nsec everywhere. On web I use nostr:npub1getal6ykt05fsz5nqu4uld09nfj3y3qxmv8crys4aeut53unfvlqr80nfm extension for nip-07. On iOS I use nostr:npub1tnpfz60snm7ler8k8c69335n37we6690qttl88t556yzkjxhahjq3kkkpe. nostr:npub1am3ermkr250dywukzqnaug64cred3x5jht6f3kdhfp3h0rgtjlpqecxrv7 uses nip-55 and is what I use on Android. https://nsec.app works for any platform.