Thats because it wasn't as well known, Older synths and Cordovoxes had no programmability that could be added beyond the sounds they came with and those were far limited in comparison.
Play with your 4X on nothing but factory sounds... then play with them using a Richard Noel or Mathis set, you will see that:
1. They don't really do anything all that special with their programming and...
2. The sounds are FAR superior than full factory only and that this is the way they SHOULD come from the factory.
Comparing a huge keyboard to an accordion is not making that large keyboard in to an accordion. Some people have the gift of being able to move back and forth between full sized keyboards and digital accordions... unfortunately, I feel that I am the majority in that if I want to play a digital accordion, I have no desire to connect to an external 44-keyed arranger.

. Thats not to say I'd not consider an arranger from Korg that takes that keyboard off and makes it 1/4 the size and lower in price, but then again, I'd likely still continue the path to programming my 8X... it's fun and educational, and let's me get the most of my financial investment.