Giant sycthes are impractical because they are absurdly top heavy and extremely unwieldily when used by an actual human being who has to follow the laws of physics.

Halberds are far less top heavy, far easier to wield, and can be used for stabbing as well as slashing.

Now, Kama on the other hand, actually are practical and useable weapons. Got a pretty long history of use going back to the Okinawan roots of Karate, resisting the oppression of Samurai after basically all obvious weapons were banned.

Kama are basically hand held miniature scythes used for farming, but they are absolutely usable as effective melee combat weapons, particularly when wielding one in each hand.

More versatile than two daggers in that you can actually block or redirect slashing attacks from swords, even lock up a spear or sword thrust if youre skilled and well practiced.

The problem with kama and many other actually quite practical melee combat weapons is that basically the combat style is much more technical than what any game has so far figured out how to be able to make work with a control scheme.

EDIT: Dear god I just noticed the double scythe. In real life such a contraption would be highly likely to result in the user of such an implement seriously injuring themselves. An absolute nonsense weapon only making any sense in a fantasy realm.

EDIT 2: While strange, a Klingon Batleth is actually a more practical weapon than a Giant Scythe in that its actually possible for a humanoid to wield such a thing without becoming immensely tired quickly, and it doesnt leave huge openings if an attack misses or is blocked, being able to more easily maneuver into a block or other attack.

…that does no damage if you hit them with the stick end 😂