I may get flamed for this but a training contract has its reasons.
In todays age people know what they are getting into when they take a job they have researched it inside and out and if you dont know that XX regional sucks by now then you may never know. So you have done all your research and you have heard 500 people tell you the company sucks and that the works rules are non existent and you are worked to the bone and you decide to take the job. You read over the contract and sign on the dotted line and the company puts thousands of dollars into your training only to see you walk away without them getting their worth out of you. I think it is unfair to do that to an employer.
If you get blindsided or the job completely changes from what you had been told by others or there are unforseen circumstances then it may be a different story.
A bad reason is taking a job at TSA or Big Sky because they are the only place you had the mins for and then leaving when you get the mins for a better regional and trying to find a way to break the contract