I don't see much hardship changing SSR code when you also have to change radio frequency
The xpdr doesn't always sit on the central radio stack. It is sometimes found beneath and to the right of the RHS yoke. Also if you happen to use one of these while hand flying the plane by yourself:
You'd be spending a good 20-30 seconds twisting those knobs to get the right number and maybe not looking out the window.
In many other countries it is not a problem as it is usually set once and we leave it there for the flight.