This is where IMHO the ULCC's in the US have lost their way. They're unique benefit is the non-stop routes. Even using smaller airports is a benefit to the infrequent traveler as easier to park, travel into/out of. I even fly them when a nonstop with a reasonable frequency is available. They seem to begin this way, but migrate towards competing with the legacies to earn "business travelers" etc and then find out the legacies will defend their turf and have other revenue streams to support them in the aggregate.

Now if your going to do a nonstop thin route, you at least have to be dependable. When you strand people for days/weeks on routes that there is no other option, it makes people leery to try again. So to run a successful ULCC you need to find non-stop routes that bypass the big cities and run a stable operation.