It all has to do with valuation. There's no fair or unfair bit about any of it. 40 years ago, pilots were valued, and worshiped like Gods. Most had paid their dues for it, too, as there were no "zero to hero in 6 months" pilot mills. People- both airline management AND the public- valued pilots, and they were paid and treated very well.
Today, we're simply not valued, either by the public or, especially, airline management. The public thinks of us as bus drivers (and nevermind the fact that most bus drivers are paid better), and airline management has quickly figured out that if there are pilots willing to work for less that they'll certainly take advantage of that.
Above all else, it's supply and demand. There are too many "qualified" (and yes, I use that term by it's bare legal definition) people for too few jobs. That causes downward pressure on wages. Combine that with the fact that many pilots will sell their grandmother's soul's for a chance to be an "airline pilot," and it exerts even more downward pressure.
Look at this from a different light. I used to own a restaurant. We paid our dishwashers $10 an hour, because, frankly, you can't find anyone who doesn't suck who will work for anything less. Now, believe me, if I had a guy come in, who had a dishwashing license, had been to dishwasher school, and who was willing to PAY ME $10 an hour for the "privilege" of "gaining experience," that I'd jump on that in a second! Look at the parallels, and then you begin to understand why our profession is where it's at.
Also note, that this phenomenon is not solely limited to aviation, but is rearing its ugly face in many professions, and this is a long term problem that this country has to solve if we're going to have any hope at future stability.
For me, I love flying airplanes, and I still have some hope for the dream of making decent money, sooner than later, flying airplanes for a living. At some point, however, you have to be realistic. I have multiple skill sets, and if I can't make enough money here, I'll make use of those other skills where I can.