The ISPs are not going the break their backs to actually block customers from those sites (Pirate Bay is first, but I bet there'll be more to follow). They just want to be able to tell the court or whoever is ordering it that they've done as asked.
It's up to the court to specifically ask for all others domains and means of access to be blocked. After all, it's the legal lot that use the specific, anally pedantic language, so why not play them at their own game? Especially if it may lose you business
