They only remove it from servers who comply to the EULA. Already atleast 3 threads on this topic found on MCM.
1.6.4 isnt a bad version though, you can still have some pretty good minigames on it. and maybe a protocall hack for some other versions to join it.They added it in one of the snapshots; the problem with this was that only newer minecraft versions (1.9.3+) would be affected by the blacklist. Blacklisted servers could just stay on e.g. 1.7.10 and wouldn't be affected by the blacklist.
They then decided to remove the blacklist from the minecraft code itself and add it into netty - a protocol framework which is used by all minecraft version from 1.7 all the way up to 1.9. The "new" blacklist would blacklisted servers only allow to stay at 1.6.4 or below.
