Junos stores the user login plaintext passowrds in the form hashes using MD-5 hashing algorith. Theses hashes are visible in configuration and starts with "$1$". On the other hand the TACACS+ / Radius Server key and VPN Pre-shared key are stored in reversible encyption hashes and these hashes starts with $9$ (Sample config att). The reversible encryption hashes are easily decrypted to origional keys using online available tools .
My question is what's the technical compulsion behind storing the authentication keys in reversible encryption hashes and is there a way to avoid this and use MD5 instead .. ?