If you want to purchase commercial porn, you need a credit card. To use a credit card, you must reveal the verified identity associated with it. To answer your initial question, my point was to draw your attention to the many interactions you already accept that are strongly associated with your legal identity. Personally, I would rather not give up my legal identity just to buy groceries from my local corrupt corporate grocery store, and I find that a LOT more invasive than doing so for porn.