Some months ago blockchain.com makes a giveaway. $125,000,000 dollars in stellar. The idea was $25 for each user. But when you try to claim the money they ask you to verify your identity.
I have account there, but I use it very rarely and my balance is always very low - I never trust online wallets, and it will not change in the future. I was not familiar with this giveaway, but I bet 25$ seemed very tempting for some users. In some way they pay you for KYC, but at the end all centralized exchanges will have to implement KCY&AML laws and regulations at one point.
Some exchanges will simply force users to do that if they want to continue to trade, others seem to have a different approach. The amount of money for this giveaway is probably symbolic, and I bet it is not only from blockchain.com wallet. This was a smart move from Stellar to promote their coin, they pay to be listed there, and they probably pay for extra promotion.