Sure but Jetstar and the others have very clear policies in black and white written on their website on the emails they send on the ticket. Its not a trick I found it pretty clear.
I understand what you're saying but ultimately its up to the person buying the ticket to check what the catch is or if there is one. A mini due diligence before hitting the pay button. No point then fronting up hoping for the best and losing it when it goes as per the details on the website!
Then ruining everybody's day by having some sort of a spack attack!