Everything on STEEM is pseudonymous. Unless you give away personal details on your own, the blockchain never asks you for anything. The data mining is done independently by individuals. The blockchain doesn't ask your birthday, location etc and doesn't tag your face on photos and doesn't recommend you friends and other stuff on your feed. STEEM is less invasive on your privacy than Reddit which ask for your E-mail.

STEEM asks for nothing. If you proactively give away information, that's the individual's responsibility. There is also no veil of feigned privacy on STEEM. Nobody guarantees you privacy except for encrypted memos. There are no ads.

Data mining is expensive and there are only very few avenues to profit from activities on STEEM (unless some idiot start publishing their home address and stuff)

There is a massive difference between a product designed specifically for the purpose of data mining and ad selling Vs a product that is immutable and fully transparent distributed ledger which anybody with an internet connection can look up.