The other point of view is that parents splitting up is very traumatic on kids, so effort should be spent on trying to avoid that. A promise to stay together (marriage) is one possible way to try to avoid that.

I don't think courting is trying to front-load the effort, but rather to avoid back-loading effort. Raising kids is a lot of work, and to prove that the two of you are willing to put effort into that, you put effort into planning cool dates while courting. Once the kids come along less effort is spent on cool dates, and more effort is spent on the kids.