Here's something I keep wondering: isn't CRISPR part of the bacteria immune system against viruses? What prevents us from directly weaponising it agaist HIV or

Here's something I keep wondering: isn't CRISPR part of the bacteria immune system against viruses? What prevents us from directly weaponising it agaist HIV or similar viruses? I guess the external membrane does, and CRISPR thus needs to be present inside of the cells before they become infected? Is the delivery mechanism once again the limiting factor?