Why Vitthal and Rukmini are separated?

Why Vitthal and Rukmini are separated? After the boon Pundrik asked (he asked Lord to stand in the same posture always for him as he loved this pose), Lord Vitthal remain as it is. When Rukmini ji asked what I will do, Lord told her to stand there only (which means a bit far as she was standing). Since then they are separately standing in this form of God.