That's not really true. Google & Facebook only sell targeting for a reason: it's more profitable than selling the data itself. Why would you sell the user data

That's not really true. Google & Facebook only sell targeting for a reason: it's more profitable than selling the data itself. Why would you sell the user data you worked so hard to collect when you can sell targeting on it again and again? It's actually in Google & Facebook's interest that no one except them have data on you.