1920 Chicago Condo.

Our kitchen sink drain is about 24" off the floor as opposed to the standard 18".

We are having the kitchen cabinets replaced and the installer is making noise about needing us to move that down.

1) Is he just whining or is there a legit reason to lower a sink drain?
2) Is this a horrible task? Should we expect to have to move the neighbor's drain down since we share a wall?