It's a balance between compactness and ease of converting to binary. The switches on the front panel are in binary. It's a lot easier to convert octal to binary

It's a balance between compactness and ease of converting to binary. The switches on the front panel are in binary. It's a lot easier to convert octal to binary than hexadecimal. For example: 0o13 -> 0b1_011 versus 0xB -> 0b1011