Well if you miss the first leg, it'll be pretty difficult to use subsequent legs anyway.

No, people used to do this a lot because of airline pricing oddities.

You'd book from your home airport --> your destination --> Tiny Airport X, then skip the second flight, because the price would often be much cheaper that way.

Called "skiplagging": https://www.bbc.com/worklife/article/20190226-the-travel-tri...

But that's not skipping the _first_ leg.

I had a family trip where it was suddenly required I show up two hours earlier, and the original airline didn't have a flight that would get me there.

I booked a one way ticket on another to make it work, then was surprised when I tried to return home that I no longer had a valid ticket for the first.

Of course, they'll helpfully offer to let you buy a one-way ticket at the counter, 90 minutes before departure, at maximal pricing.

Met a guy who had to fly Munich→Frankfurt→Munich→New York City, because it was considerably cheaper than just Munich→New York City.

He would have gladly skipped the first 2 legs of the trip.

This is because sometimes the airliner sell a flight connecting through your departure airport for less than a flight departing from it.

Let's say you want to fly from Vegas to New york, it might be cheaper to buy SFO to new york, and hop on the Vegas->Mew York leg. They essentially make this option less viable, and can price each market differently.

That makes sense. For me, what happened was I was scheduled to fly to a destination city but wound up flying there from a different departure city, earlier, due to a funeral. I was shocked to find out that they would have cancelled my return trip as well if I didn't call in to grovel.