Wrong now? or wrong in 1973?

What is your concern? Certainly wouldn't see that today with the current NEC code but existing homes are grandfathered until you do additional work which then requires bringing it up to current code.

I'm selling the house and I'd rather not have to redo wiring. The bathrooms are the only thing that seem to be miswired according to current code. I've updated them with new toilets and vanities but not wiring. I guess my concern is the future buyers inspection.

You're not required to bring it up to current code if you just replaced the vanity and toilet. It would have needed to meet the code at whatever time the work was done.

The home inspector may quibble, but that's the reality of construction. Otherwise we all would be ripping our houses apart with every code change.

I can not imagine the home inspector is going to map out all of the circuits in the house. He will check for GFCI protection where currently required (but maybe not when built) and verify that no wires are doubled up on breakers or connected to oversized breakers. That is about it I would guess.

'no wires are doubled up on breakers"

Some breakers are listed for double tapping.
Ones that are not you just use a wire nut and a pigtail over to the breaker.