I often see that the "traditional" weapons of China/Korea/Japan are full of swords and Spears like the Chinese jiang or the Korean Woldo. We also see some "systems" develop like the chinese folklore weapons (the Jian, the Gun, the Qiang and the Dao)
But where do maces and axes fit in all of this? We see them being used extensively in Europe, pre-columbian American civilizations, the middle East etc. Etc.
Why aren't these weapons as prominent in East asia?
They not prominent because our image of East Asian weapons is dominated by relatively recent weapons. What advantages do axes and maces offer?
Some of them are more effective anti-armour weapons than swords and spears. As guns became common on battlefields, halberds and maces became less common. If many soldiers are carrying very effective anti-armour weapons (guns), or armour itself has become relatively rare on the battlefield (due to guns), heavy polearms and maces become less useful, and soldiers will tend to use spears and swords instead.
Axes and maces can be a cheap alternative to swords. A light battle axe can be made with much less iron and steel than a sword. A all-iron mace can be an effective weapon (and with a wooden haft, can be made with less iron than a sword), while good quality swords require steel (at least for the edges). As iron and steel production increases, the number of axes and maces compared to swords can decrease.
So if we build our image of Chinese and Japanese weapons on the Qing and late Sengoku Jidai (and Edo) battlefields, we might expect to see relatively few maces and axes. Rather than comparing these East Asian weapons with Medieval Europe, we should instead compare with Early Modern Europe. In both cases, we see plentiful guns, swords, spears, and relatively few maces.
If we look earlier in East Asia, we see plenty of maces and axes. For example, in ancient China, we see the ge (dagger-axe) as a very common weapon on the battlefield, in both two-handed long polearm forms, and as one handed battle-axes:
and many axes:
http://www.arscives.com/historysteel/cn.bronzeweapons.htm (items 27-30)
http://www.arscives.com/historysteel/cn.bronzeweapons1.htm (31-32)
http://www.arscives.com/historysteel/cn.steelswords.htm (83)
Later, including into the Ming Dynasty, we still see many axes and maces:
https://commons.wikimedia.org/wiki/File:Ming_mace_and_axe_cavalry.jpg
https://commons.wikimedia.org/wiki/File:Three_Brothers_during_the_Yellow_Turban_Rebellion.jpg
https://commons.wikimedia.org/wiki/File:Wujing_Zongyao_maces.jpg
Probably deriving from Ming usage and Ming literature, the "18 weapons" ("18 weapons of kung fu", "18 weapons of martial arts", etc), a conventional list of weapons that should be learned (at least in part) by skilled martial arts includes many axes and maces. The actual weapons making up the list varies, but typically about 1/3 to 1/2 of them are axes or maces of some type.
As such weapons largely disappeared from the battlefield, they remained as martial arts weapons (as exotic weapons, rather than everyday weapons).
A variety of weapons which can be classified as maces remained in use in both China and Japan: the jian and bian sword-like maces (often called "sword breakers" or "iron whips"), iron rulers, sai, jutte/jitte. The Ming Dynasty versions were often brutally heavy two-handed maces, and their later descendants were often much lighter iron truncheons, used for police work (as parrying implements and as less-than-lethal weapons).
