Modern cryptographic algorithims rarely get broken, but keys get stolen by malware all the time. Instead of moving the keys out of system memory and thus out of reach of malware they just add layers of obfuscation to a key that is going to be decrypted into system memory. Mixing unrelated strong ciphers is likely to yeild nothing but a false sense of security at best and yeild malleability attacks at worst.

If you take your key and encrypt it 3 times, or 200 times, it is still moot if it by design it ends up plaintext in system memory.

You don't see anyone else doing this sort of nonsense mix and match security for a reason. Their threat profile is fundimentally broken if they think attacks on modern crypto primitives are more likely than malware on an end users system.