DuracellEnergizer said:

Mavericks said:

So, if you decide to freeze Han, just take him from the cell, separate him from his campanions and made the rest of your job. Why should Leia, wookie and even robots be kept together in all their way to the Carbon Camera?

For emotional resonance. The scene wouldn't have much in the way of gravitas if it was just Vader and a few ugnaughts in the room dipping Han into the vat.

Plus Vader gets to finally see the droid he created as a kid named C3PO.

Another ridiculous PT nod to the OT Lucas created!