I expect this has more to do with expectations about compatibility and the strength of the relationship, rather than actually stronger relationships. It would be interesting to see data on subjective satisfaction, behavior, etc. that would separate out couples who are staying married out of duty vs. couples who actually like each other.
Analyses I've seen say this has a lot to do with expectations, but in a rather different way than you described.
To get things out-of-the-way: All the data I've seen suggests that couples in such countries DO actually appear to have stronger relationships and people in relationships DO appear to like each other more (at least a few years in).
General analysis:
US: Couples go into a relationship with the expectation of a Disney-style romance, with a soulmate, prince charming, and all that. Sometimes, that's even there up-front, but people change, and 10 or 20 years down the line, "soulmates" will usually be less compatible. At that point, people are hit with disappointment, conflict, and quite often, divorce. The expectation of potential divorce also gives less incentive to invest into the relationship too. That's especially true in times of crisis. If you're hit by a car, does your mate stick with you or move on? People need to hedge.
PI: Couples go into a relationship with the expectation of initially being different, but of needing to the work to make it work, since they're in it for life. They're not disappointed when reality doesn't look like Disney, and usually they work together to make things work out. Couples tend to grow together over time, rather than grow apart, which is a healthier dynamic. In crisis situations, couples can count on each other to have their backs, since if things go badly for your partner, they go badly for you and vice-versa. Plus, you'll be counting on them in 50 years, so if you're not there for them now...
Refs: Modern Romance by Aziz Ansari.
But there is a more general aspect that parents can objectively evaluate compatibility and quality of your partner in a way that you can't. Again, it's worth noting there's a scale here. Do you inform your parents? Get advice? Ask permission? They pick, with your permission? With your advice? Entirely arranged? It's a spectrum.
