1979 Bogner Modded Marshall (Pics)

[EddyLenz]

I would assume the reason is that he wanted to keep the audio signal on the board and not having it go back and forth to/from the switch.
At least this is what i understood why you want to have relays on the board: To keep the audio signal on the board and with short signal paths and only have the control signal "travel" to the switch on the panels. Also helps to avoid shielded cables if you have signals in the part of the circuit where you want to avoid exposing them to outside interference. In the picture of this part of the circuit you can already see several shielded cables so i guess Reinhold wanted to avoid the audio signal also to have to travel to the switch.

That would be a good reason if it were switching something in the direct signal path that wouldn't otherwise need to leave the board. Here, though, it's only switching something on the cathode of a gain stage.

 

[Infernal_Death]

Ok, then i agree it seems like an odd choice.

 

[ST.KTULU]

Wow!