You do realize that a Priest merely WITNESSES a Catholic wedding. The Sacrament is actually performed by the Bride and Groom. Many of them know full well that the marriage itself is not valid at the time of the ceremony or soon there after.
And don't they feel silly -- but it doesn't matter. However stupidly you enter a contract, if you sign your name on the dotted line, its binding.
Doubly so for a contract sealed before God Himself.