For later.
Wondered this myself. Though I think everyone agrees that the US Church often uses annulments as a Catholic divorce court.
And/or American Catholics are such damaged individuals, that they routinely lack either the intellectual ability to comprehend, or the psychological ability to commit to, an actual vow.
Slightly /s/ -- I'm making the point here that these people seem to have the capacity to enter into a 30-year mortgage, co-sign on a RV, sign a contract with the U.S. Marine Corps, beget and raise children, share a checking account, etc.etc., but supposedly lack the maturity to say "I do" --- and be done.