The driver tube plate resistors connect to the B+ and relay its full voltage to the grids of the output tubes at turn on.  By the time the driver tube comes on line, it is too late for the output tubes and possibly the output transformer. Staggering the turn on of the tubes would help, but do nothing for a driver tube failure, domino like, cascading into the output stage, or help when the driver tube is jiggled or removed from its socket, or when a brownout has greatly reduced the B+ voltage but not reset the staggering sequence. Coupling capacitors and interstage transformers do not look so bad now.

   One comprise is to use cathode followers between stages. Yes, this does introduce yet an other component in signal chain, but it protects against tube startup and removal. The better idea is to use coupling capacitors with the cathode followers, shifting their place to the front of the cathode followers. With this setup, much of the coupling capacitor's and the direct coupling's disadvantages disappear.
    By placing the capacitor on the other side of the cathode follower, it cannot be excessively charged positive by the output tube going into positive grid current when the amplifier clips, which would make for a blocking distortion from