Robby Roto does save scores....
Gorf/Wow both have the memory write protect circuitry to make HS saves possible, but didn't put a battery on the board, and clear the HS table at boot.
I started looking into code mods for gorf a while back, but the code is wretched to read through, since it's obviously compiled code rather than hand-written assembly.
There's no actual 'startup' procedure like most games have... if you reset gorf, it just restarts on the current level, instead of going to attract mode.... it's quite sloppily coded.
In any case, adding HS saves would probably require replacing the ROM board entirely, but considering how crappy the sockets are on those boards, it's not a bad idea anyway... heh. Of course I made replacement ROM boards about 5-6 years ago to fix my robby roto, so at this point, it'd just be a matter of hacking the code -- but I doubt anyone wants to pay for a complete replacement ROM board,and will expect a $45 kit like all the other high score saves, so it hasn't been a particularly high priority.