Back in reality, people miss flights all the time. Not only are you not banned from flying the airline, you often get a credit that you can apply for your next flight.
It does depend on what kind of ticket you're travelling on, and what restrictions apply to it.
Full disclosure: I have a bit of a history of flying on what some call "mistake fares". Back in 2013 I flew "from Europe to Hong Kong and back", except it was routed via Australia(!) both on the inbound and the outbound. Was convinced I was going to be denied boarding at every single stop on the itinerary ...
But were you actually denied boarding, or just worried about it? The restrictions may affect what kind of credit you get for missing a flight, but you will never be banned from flying the airline - that's absurd.
Airlines don't have to honour mistake fares, and this was definitely one of those. FWIW, I got away with it.
If you miss a flight and the airline determines you booked it (typically as a return or hidden city leg) without ever intending to fly it, they will very definitely try to make life difficult for you.
Try short-checking a bag to LON on a NYC-LON-Europe booking with AA or BA, they will refuse. They're worried you booked to Europe for a lower price but intended all along to leave in LON.
There are ways round this "rule", too. If you know what you're doing.
Full disclosure: I have a bit of a history of flying on what some call "mistake fares". Back in 2013 I flew "from Europe to Hong Kong and back", except it was routed via Australia(!) both on the inbound and the outbound. Was convinced I was going to be denied boarding at every single stop on the itinerary ...
I was also younger and fitter then :)