Thats not actually true, they have character services sales more often then that
June 2013
https://worldofwarcraft.com/en-us/news/10158003
October 2014
https://worldofwarcraft.com/en-us/ne...-sale-extended
March 2017
https://worldofwarcraft.com/en-us/news/20602174
June 2018
https://worldofwarcraft.com/en-us/ne...e-back-weekend
March 2019
https://worldofwarcraft.com/en-us/ne...-game-services
Probably more I didn't find a link to immediately.
These sales usually don't coincide with other sales like this one, so you won't see them around black friday, christmas, or whatever, but they definitely do exist.