Code makes or breaks any reasonably modern pinball. But it's a lot easier to revise than a layout that can do the same.

Some games offer a lot to shoot at, but reward repeatedly shooting a safe shot over and over again to score big without trying for any other goals. One that comes to mind is Hook - just shoot that left spiral ramp, it sends it the right flipper, rinse-lather-repeat. As opposed to another example from the same era with a similar left ramp, Creature from the Black Lagoon. You can do that all day too, but unless you are in multiball you are not accomplishing anything shooting it on its own. CFTBL's is coded to make you shoot something else, as that ramp combos with the center lane, and you have to shoot everything else on the board to get a multiball. Of course you can shoot the center lane repeatedly and score big in the Move Your Car mode, note it's a harder shot to make repeatedly, but still one of the safer shots on that game.

A code revision might lessen the importance of a particular shot. Suppose Creature had a revision that made you do something else (perhaps start multiball or shoot the sometimes-draining snackbar) before doing MYC a second time, that would change my strategy if I went in with the intent of blowing up the center lane repeatedly for high scoring. Also, sometimes code gets revised for tournaments. High Speed has a tourney version that disables the progressive multiball jackpot that normally builds between games. Some owners at home use that, since progressive jackpots are only a useful feature on location.

One thing to remember, especially with pins from the 90s and before, is they were not built or programmed to be played by the same person/people repeatedly like video game consoles at home, but by many people for short times in a location. Now that there are more pinballs in people's basements and man/ladycaves than in the wild, and collectors buy a larger amount of new pins, code will always be tweaked (or have owners wanting it) to maximize the experience that the cabinet can offer to someone who has made a big-ticket, longterm investment in a game.