There's benefit when working in low-security environments. A custom crypto model will make your process harder to understand by a reverse engineer. This adds so

There's benefit when working in low-security environments. A custom crypto model will make your process harder to understand by a reverse engineer. This adds some security by obscurity, but almost certainly weakens actual security. Let's say you just want to store and restore data on a user's computer, but want it to be difficult to read by an outside program. In this scenario, using an established algorithm makes it easier to decipher your encoding, and by nature if the encryption and decryption happens on the user's machine then you have to store the public and private keys on the user's system. There's no other way to accomplish this task if offline is a requirement. So in this case, obscurity has value in deterring reverse engineers.