Church law on divorce and remarriage refuses to accept the plain fact that some marriages fail. It insists that two people who no longer live together, may not communicate except through their lawyers, are actually still married. In the real world, if a theory does not match reality, it is (or should be) discarded; but the unmarried men who make the law refuse to give up their theory, even though it does not fit the facts very well. 

Moreover, the lawyers say, "One size fits all". No matter why the marriage failed, if one remarries, one is excommunicated.