The involvement of the priest in an RC wedding is relatively recent in church terms.
He was often/typically an honored guest, and would bless the marriage.
It wasn't required that he witness the vows until the1300s or so, to deal with the couples who disappeared, returned, and told different stories as to whether or not they'd exchanged vows.
This led to a new abuse, in which the couple the couldn't get their families to agree would break into the rectory, wake up the priest, and exchange vows before he'd come to his senses.
This was corrected a little faster--a mere 700 years--in the late 20th century (1979?) revision to the code of canon law.