This rule only applies to a single adult + child pair, and not the entire traveling party. For instance, if you have a party of 1 child and 2 adults, the airline is well within its rights to charge seat selection fees to the second adult. It’s incredibly frustrating that I have to pay an extra $40-$50, per journey, to United to sit next to my wife and child. And that’s with the current “consumer friendly” rules in place.

I usually filter out all Basic Economy fares from my search and only look at the next tier up, where you can get seat selection at time of booking. I just figure it's a product that doesn't work for my family.

I have to pay more to select the exact seats I want on a plane, so why shouldn't you?

Think of the inverse, someone who doesn’t care about where they sit save money.

On the other hand, I never understood this obsession with grown people acting like it’s the end of the world if they don’t sit together. My wife and I fly a lot together - over a dozen trips this year - and she flies more frequently by herself. We both prefer window seats. We hardly ever sit together unless we can get 2 seats next to us by ourselves like on larger planes with a 3-2-3 combination or exit row seats in main.