I'm certain the high cost of a college education is a big part of it.
Parents who paid for tuition out of savings or went into debt taking out a second mortgage are likely to view their unemployed graduate as being a "slacker" or unambitious at the very least.
They're thinking: "We spent all that money and he/she isn't working!"
A lot of people expect college graduates to have a job lined up after graduating. Some of them actually do because they worked internships during the summer for companies who will hire them after graduation.
In my mother's household when you finished high school you were suppose to be gone period! Whether it was away to college, the military, or found a job and got your own place to stay.
You weren't expected move back home either!
A parent might see a child with a $100k in debt kicking back at home watching daytime TV and emailing resumes while waiting for a call. There's no sense of "urgency" or "determination" seen.
Their thought: "You need to find a job while you're waiting to establish your (career)! You're not going to just lounge around!"
The sad thing is many people actually wasted both their time and money on degrees which are "NOT in Demand" when it comes to earning a high enough salary to payback their loans and live comfortably. A parent may also know of some other child who became a union electrician or plumber that's earning over $100k and they're comparing him to their child who has a bachelor's degree in African Studies or psychology and is unemployed.
Whenever people don't see a return on their money or time they tend to lose their patience.
Also there may be some grads who have "unrealistic expectations" who thought their degree was going trump experience in the industry and everyone would be clamoring to hire them offering a high salary and private secretary....etc
When this doesn't happen some go back to school to get their Masters or earn a PhD which increases their student loan debt.
In today's climate a student has to be networking and making moves before they graduate! It also helps to be open to relocating to any of the 50 states for an opportunity.