Why do people expect something for nothing?

As a freelancer on Upwork, I am fortunate to have a well paying ongoing gig, which earns me enough to live on. However, occasionally browse the jobs going on Upwork and other freelancing sites and think how lucky I am.

Consistently, I see potential clients expecting to hire freelancers for specialised, skilled work, and pay them the equivalent of $3 an hour or less.

What also makes me laugh is how the client will say that they need someone who's an "Expert" or "Intermediate" level in that profession, but expects to pay them peanuts.

What could be causing this mismatch between expectations and reality.

If I was going to hire a copywriter to, for example, write me a 300 word Steemit article every 2 days or so, I'd pay them the equivalent of $20 an hour for their work, as I'd expect quality and would be getting a return for my investment.

Likewise, if I needed someone to build me a bespoke php/mySQL website for my business, I'd pay the going rate for a php developer with web design skills, or access to their own designers, and I'd expect this to be built into the price.

Interested in hearing your views on this. Have you had experience with ridiculous expectations? Have you found it hard to find a well paid gig as a freelancer?