Or maybe they picked them out loud in class, and some of those were deliberate responses to others.

So what happens is: Albert is an oldest child whose younger sister is loud and annoying and gets all the attention. He says "I'm going to write about how being an older sibling is hard". Beth is a youngest child whose older brothers get all the new clothes and toys and things; she gets their hand-me-downs. She thinks Albert's got it all wrong and, determined to set the record straight, says "I'm going to write about how being the youngest child is hard." Charles realises that as a middle child he has all the same problems Albert and Beth do, and misses out on some of their advantages, and says he's going to write about that. Diana hears all these and thinks, "Well, at least they have siblings to play with and relate to", and announces her intention to explain how things are bad for only children.

Notice that all these children may be absolutely right in thinking that they have difficulties caused by their sibling situation. They may also all be right in thinking that they would be better off with a different sibling situation. (Perhaps there's another youngest child in the class who loves it -- but you didn't hear from him.)

In my small fourth grade class of 20 students, we are learning how to write essays, and get to pick our own thesis statements. One kid, who had a younger sibling, picked the thesis statement: "Being an older sibling is hard." Another kid did "Being the youngest child is hard." Yet another did "Being the middle child is hard", and someone else did "Being an only child is hard." I find this as a rather humorous example of how people often make it look like they're being oppressed.

Does anyone know why people do this?

it's generally better to donate $X than it is to volunteer $X worth of your time

In what sense is this better?

Consider a diehard Democrat volunteering for the Obama campaign. He's perfectly willing to spend six hours knocking on doors (for free), because he enjoys spreading awareness and bonding with his fellow Democrats. But to hire someone to do it (for minimum wage), he'd have to donate ~$50, which he might not be willing to part with. So in this case it's much better for the individual to volunteer than donate. It's also better for the Obama campaign, because they'll get more mileage out of someone who did the work for fun than someone who was primarily motivated by the cash.

The only person who is worse off is the hypothetical paid person who Obama would have hired instead. But the volunteer only cares about himself and Obama, not some random person who needs a job.

Yeah, but nobody's going to think that if the service is offered for free.

Yeah, nobody in their right mind would highly value things like Linux or Wikipedia... Or the Sequences, for that matter.

By charging a certain amount you tell people how much they should value your product.

At most you can do some anchoring. You can tell people how much they should value your product and people can (and often do) disagree with that.

If you charged a $200/hour "consulting fee," people would see you as professionals, and value your advice highly.

Conditional on those people first deciding that these two guys are worth $200/hour.

CS grad student here. Some mistakes I made were

• Not documenting code.
• Naming figures/datafiles poorly, so that you have no idea what they are in two weeks. It's best to have an automated way of labeling files if you'll be creating a lot of them.
• Storing data in an inefficient way (very bad if you're generating large amounts of data).
• Not using version control.
• Diving right into implementing an algorithm without first thinking about whether that's the best way to solve the problem.
• Being intimidated by tasks that looked difficult (they were rarely as hard as I thought they would be).

Most of the students who we advised said that knowing what they know now, they would have sought advising from us only if it were free.

I think this is precisely because you aren't charging for advice. If you charged a $200/hour "consulting fee," people would see you as professionals, and value your advice highly. But now that you're giving advice for free, you're just some random Internet guy telling kids how to run their lives.

High school and college students generally don't have much money.

Well, you market it to the parents. People pay for college admissions consulting all the time.