The reason that service is awful is that the traveling public refuses to pay for good service.
If Airline A has great service and Airline B has bad service but their fares are $10 cheaper, travelers flock to Airline B. That means that Airline A risks losing its customers unless it matches Airline B's lower fares. Of course, Airline A can't reduce its fares and maintain the good service without losing money. So, they cut services, lay off employees, cut employee salaries, and become just as lousy as Airline B. However, they keep their customers because the fares are now cheaper. The customers will complain to no end about the bad service, but they won't pay a few extra bucks to get good service.
The end result is a race to the bottom. The airlines have simply given the public what it has asked for.
Just take a look at this website. How many questions start with "what is the absolutely cheapest fare to [fill in a city]?"
I would say that it is for the same reason that you can't get consistently good service anywhere anymore. The service industry just isn't what it used to be and neither are the people working in it. It really is a shame to feel like you are taking up someone's time when all you are asking them to do is their job that they applied for, accepted and get paid to do.
because they know that many travellers are dependant on them for cross-country/ international travel. if you have a guaranteed customer base, no matter how badly you treat them, then why try?
Because of a whining, sniveling public that demands cheap airfares.
Service comes with a price, and the public doesn't want to pay it. They want cheap, so they get cheap.
Three airlines just went bankrupt trying to please a public that won't pay for what things are really worth.