An aside but some years ago I was taking a flight in Europe and I was fascinated to see the differences. It seems many budget airlines operate on a similar mode

An aside but some years ago I was taking a flight in Europe and I was fascinated to see the differences. It seems many budget airlines operate on a similar model but the EU has steep fines for late flights so there's a huge incentive to find alternatives. In my case the alternative appeared to be an entire backup airline that seems to exist only to serve other airlines when they experience issues. A plane was quickly scrambled from (IIRC) Lisbon and flown to Heathrow and we were all shepherded onto it as quick as they could possibly manage. The plane was garbage, service was garbage and food was garbage but they did get us in the air quickly. Ultimately they missed their 4hr delay window by about twenty minutes so I was entitled to something like 600EUR of compensation anyway. I imagine there are a number of reasons why this wouldn't work domestically in the US but without the threat of fines there simply isn't any incentive to provide it anyway.