The people using these generally have no clue they are pirating. It is just this box they bought that offers great value.
This is what has replaced Bittorrent because it is immediately accessible to the masses for $199 or whatever those boxes cost.
some addons that are just fronts for piracy sites that host videos but there are some that use Bittorrent to stream content.
getting a box is extremely cheap too. buy any chinese android box and connect it to your tv and you are good to go. but more mainstream there's people who buy boxes, install the addons and resell them at a higher price to people who don't want to mess with technology.