And no, I don't mean because wedded bliss sometimes gives way to wedded blitzkrieg...
Look at it this way - receiving the Sacrament of Unity when there is no unity, seeking to hold the Host when you don't hold to the teachings about grace and sin which the Church hands down from Christ, partaking of the Wedding Banquet of the Lamb without submitting to His leadership, enjoying the Bread of Heaven with the Mystical Body of Christ the tenets of which you don't fully espouse?
Why, it's kinda like enjoying the marital bed with a partner you haven't fully espoused.
The outright lie you tell with your body by presenting form Communion when you are not in union with the Bride of Christ is, perhaps, the same lie you tell with your body when you have conjugal relations with someone who is not your sacramental bride or bridegroom.
Why would anyone want to tell such a lie, or to have such a lie told?