What else can Vader say to Luke to tempt him? Come to the dark side, and I'll buy you a puppy? ;)
How Luke doesn't go nuts with Vader Force messaging him all the time is a miracle. I don't think Yoda taught him the Jedi voicemail trick.
IIRC, wasn't it debated around here whether Vader's lines in that were a recent addition to make that unfinished scene more complete?