PFOF (payment for order flow) is totally separate from privacy.
It’s a way for retail trader to get a price improvement on trading, that improvement is shared between the broker and the trader.
Most retail broker will send the flow to specific venue/market makers, because it’s actually good for their users. (and they get some revenue as well)
(There’s some debate whether the split is the correct one, ie how much of the price improvement should go to the broker vs trader, but it’s generally an improvement)