Weight is a lot harder to use than volume. If I'm measuring a cup of flour (for example), I dip my measuring cup in, level it off, and I'm done. Takes a few seconds. If I use a scale, I have to watch the scale carefully until I'm getting close, then slow down my rate of pouring into the bowl greatly so that I don't go over. Sometimes I will still go over despite my best efforts, and then I have to take flour out to get the measurement right*. It's a huge faff, and it doesn't even produce a better result the vast majority of the time. Some recipes are finicky and do better with a scale, but 90% of the time volume measurements are much faster for the same result.

* and to head off the obvious "just don't worry about it if you go a few grams over" rebuttal: that defeats the purpose of using a scale for precision! So either you don't worry about the wiggle room in measurements (at which point just use volume, it's faster), or you strive for precision and it takes you much more work. Either way it's a worse solution unless you really, truly need maximum accuracy.

> The US seems to run on volume, rather than weight.

Baking is based on proportions. As long as you use the same measuring tool, the details don’t matter.

2 cups of flour works regardless of the size of your cup