Somebody should tell that to the multi-billion dollar a year industry that sprung up over the buying and selling of the most mundane details of our lives. Or maybe they should ask why basically every company everywhere spends so much time and money collecting, storing, and managing far more data on their customers (and anyone else they can) than they actually need to conduct their business. Companies don't usually like spending a bunch of resources for zero reason. The idea that "your data isn't worth anything" is demonstrably false. Your data is so valuable that it's making companies money hand over fist, and most of it that is at your expense.

Try to sell it and let me know how much you get.

Spoiler: $0. Your data is not worth anything.

You have an extremely weird idea about the relationship between “how much something sells for in the market” and “how much something is worth”. Could you answer how you view this relationship for the following things?

1. Your kidneys, or heart, or any vital organ.

2. Weapons grade Plutonium.

3. Falcon heavy.

4. A single grain of rice, 100 million times.

What you are saying implies “we don’t have a good marketplace for user data”, which is pretty obvious. But I have no idea how “thus it is worth nothing” follows from there.

I can’t pay my mortgage with a car either. Or US dollars, for that matter. Are those worthless as well?

Huh?! You can sell your car, or take a loan against it. You can convert US dollars into your local currency.

Your individual data is worthless. Data is only worth something in aggregate.

Is it not like saying that any individual worth nothing because their social value is zero outside a collective?

I can give away some data to use a service. Companies generate money using this data. It is not useless.

I’m sure the market was drunk on the day when Apple changed iPhone privacy settings and Facebook’s valuation dropped by 10 digits US dollars. /s