Mainly because it's impossible to tie a solid metric between piracy viewings and marketing impact, or at least it's difficult to the point where it hasn't been done yet. You'd need to have a pirate viewership metric tied to movie sales / streaming views and prove a correlation to assign a value that you can present to media executives.

Until that metric relationship is established in dollars and cents, the studios will ignore it, as there's no proof it's making them money. You'll note that recent releases and re-releases (cough Morbius) have spoken to the industry's ineptitude in reading underground internet trends - there's no way they'll ever look at piracy as a profit center unless you can smack them in the face with a large dollar figure.