Couple 1: bought their house in 2011, have no kids and no car (because they live in a walkable city). So they overpaid their mortgage every month and paid it off. They are piling up savings and putting a lot into their pension funds. They could probably retire by the time they're 50.
Couple 2: bought their house in 2008, so it's overpriced and small. They only bought it to get onto the property ladder "before it's too late". They had kids around 2013. So they need 2x cars (because kids) and had to buy a larger home (2x mortgages, because home 1 was still in negative equity). The rental income from their first home is heavily taxed. Honestly, I can't see how they're ever going to retire. Their 2nd mortgage will be with them until they are both around 70 years old. Hopefully their first home will appreciate in value and they can sell it. If not, it'll provide some income (rent) or a place to boot the kids out to when they hit their 20s.
Salaries in Europe are shit compared to US and I've zero incentive to move to Western Europe for the average wage I'd be making there.