because:
1- its a different game developers (and they can do with own game what they want). for example mods in WoWS moderated by developers. WoT mods not moderated
2 - WOT detects executed every week but in short time (1-2 hours per day). WOWS detects executed few days or weeks
3 - this bans only for WoWS
4 - because warpack most popular mods for this game (except HAGS and 1-2 another cheats) - developers can easy make detect for one mod. in WoT developers must make 1-100 detects for all available forbidden mods