In answer to the OP question - because the KB I have serves my needs ...
If I were still regularly playing restaurant gigs, cocktail receptions, etc. perhaps I MIGHT be looking for a new KB, not necessarily an SX900 ...
One day your here next day your gone....
Go for it always!
For those always seeking the latest and greatest (?), - not just talking about you, Donny - when the final day comes, will they be asking "Is that all there is?" ...