Just curious... Why didn't Yamaha make the CP73 with the same wooden keybed as the CP88?
That’s a “how come?” question... there are never any good answers to “how come” questions... because it doesn’t fix anything for you.
But weight might be the answer... the Natural Wood keybed (CP88) is significantly heavier (total weight) than the Balanced Hammer keybed as found in the CP73.
To make the CP73 ”...for the gigging keyboardist...”, total travel weight was a major consideration... the only difference between the units is the keybeds (number of keys, type of action, total weight)... they are otherwise identical.
The CP88 is just over 40lbs., the CP73 is just under 30lbs.