I don't think it's that. It's just what the mass market wants. For economy-class passengers, the overwhelmingly first-place concern is the price of the ticket. People accept shit service, shit food, random seat assignments, inconvenient timing and connections, etc. all for a cheaper ticket. For some people, the ticket cost is the only thing they care about.

So it's a race to the bottom. Airlines are famously low-margin businesses, so they really have no choice but to save as much money as they can by continually pushing the envelope on what depravities passengers will accept. And as they keep pushing, people complain, but they still eat it up and love the lower prices.

If economy class passengers would actually pay for perks and a nicer experience, the airlines would provide it. And sometimes they kinda-sorta do, via economy plus, premium economy, and similar (whatever the particular airline chooses to call it). But, by and large, people just care about the lowest price, so many planes don't even have mid-range service options, and some airlines don't even offer them at all.