The nature of the beast!
They don't need to pay any more. These are the market rates. The supply of labour far, far, exceeds the demand! The entire conceptual basis of low cost is just what it says on the tin. Apart from cartel costs (fuel) and regulatory costs, everything else is necessarily pared to the bone as an input cost. Aircraft acquisition, airport charges, catering, maintenance, ground handling, administration, and most certainly labour! Anybody who thought otherwise was living in a fools paradise. A decade and more on from inception, anybody who still thinks otherwise is simply delusional!
Even the legacy carriers, and particularly those operating from some of the most crowded and high cost real estate on the planet, have sought to pare down their own input costs to a level that still allows them to operate. You only have to look for such phrases as "B scale" and "C scale" etc. to see ample evidence of that.
Go over to the wannabes forums, and you will find thousands of "low hour" basic licence holders who would give their eye teeth for one of these "opportunities." It never fails to amaze me how many people seem to labour under the illusion that once they have secured such a job, their basic levels of experience are somehow going to be overvalued, and given a status that might have existed 30 years ago.
There are good legacy opportunities around the world, but often those opportunities come with their own baggage. Living in a desert (even a desert with nice shopping malls,) or a tiny apartment in a very crowded, hot and humid island, is sometimes a high price to pay for that type of opportunity. The wages and T&C's on offer, often reflect the reality of living costs in those parts of the world, and even then, the positions themselves come with the constant realisation that you are a "guest" in those labour markets.
Many of these "lo-cost" operations do have relatively poor terms and conditions attached. They have become the modern day stepping stones for those seeking their first rung on the professional ladder. It is ignorant and unhelpful to call aspirants to these jobs derisory names. That is particularly true when you do so from an experienced perch that comes with its own set of downsides, even if the headline salary does fill you with a sense of your own superiority.
For those who haven't researched the nature of the beast they have chosen to ride, then they have not been very wise, because all of the information is in the public domain. If you choose to ride, be prepared for the reality of what you are taking on, because you will not change the nature of the beast. My answer to those who bemoan the T&C's of these companies, and complain of poor pay and long hours, is "dry your eyes Princess," many of them do not want your loyalty (they have no seniority.) Their terms and conditions reflect the reality of the market conditions of where they operate. You are climbing a slippery slope and there are no safety nets. Use these opportunities wisely to get where you want to be, or more precisely where you think you want to be.