Because people don’t know how to pirate anymore. Circa 2000 everyone I knew was pirating everything. There is no Kazaa or bearshare or Napster anymore.
And even I'm kinda warry of using bittorrent... Usenet is fine from legal stand-point for sourcing my linux distros. But networks where you share got enough legal trolls to make want not bother. And I don't consume enough linux distros to make any special setups.
It is amazing what wealth of linux distros are out there for the taking. And in many cases that's the only way to get them since no one is willing to sell those linux distros to you anymore.