As opposed to what? US homes (with very few exceptions) do not get fed all three phases, so the utility company must ensure that it puts equal load on all the phases - whether it does that on a house-by-house basis or at the neighborhood level makes no real difference.
Just to be clear, that IS exactly how transformers work. A transformer that steps 220V down to 110V has a turns ratio of 2:1. It’ll step 230V down to 115V, 240V down to 120V, and 110V down to 55V.
There are some practical implementation details (actual voltages may vary under varying load due to winding resistance, maximum power handled will be lower at lower voltages, etc.) but that is in fact exactly how transformers work.
I was just thinking that, if the three legs are widely geographically separated, it’d be a lot easier for something to happen to cause a load imbalance. Like, say, a break in one of the lines, at a point that still had a lot of users downstream from it.