What's scary is the "attachment" aspect of irregular/false marriages. You get involved with a person, you get used to them, you fear being alone (if your original wife won't take you back), you might have a new house and mortgage with the new wife, perhaps she works a good job and your old wife didn't make nearly as much. What would you do?
When a person divorces, remarrying is almost a given for two reasons: loneliness, and the ROOMMATE aspect. Young people -- at least the practical and thrifty ones -- often want a roommate, because it's not economical to live by oneself. Having one other income earner living with you means you can live much better, and have some money left over at the end of each month.
If a man divorced his wife and remarried a woman who earned more, he would upgrade his lifestyle. I know several men who have done this. Especially when this is done later in life, the couple usually leads a "DINK" lifestyle (Double-Income-No-Kids) because the kids are all grown. And for those who can't guess, DINKs usually live very well. Upscale neighborhoods, lots of freedom to see the world, all the luxuries and gadgets money can buy, eat out every day, you name it. When you have no kids to support and two incomes, it's hard to worry about money unless you're horrible with money or something.
If a priest were to argue with him or try to convince him to go to confession, he would not only have to come to terms with his own sinfulness and repent, but would also have some major life changes to make! He'd have to MOVE, probably into a much lower-end home, he'd have to CIVILLY DIVORCE his existing fake wife and have legal expenses and lose much of his assets, etc. And what about all of their mutual friends they've made over the years? The people they invited over
And if it's the woman who used to be Catholic, it's even worse -- her new "husband" would be supporting her, and she would have to find a job or someone else to support her, possibly not as well as her current "husband".
It's a mess!