First, it is worth noting that not all Chinese spears and swords have/had tassels. Some have tassels, and some don't have tassels. Second, it should also be noted that many non-Chinese spears and swords also have tassels. So the simple answer to "why" is that they have tassels for the same reasons that other people used tassels on their spears and swords - when they used tassels.

Tassels on swords traditionally had various possible functions, which can be combined:

1. Ornamental. It's there to look attractive.

2. Unit insignia. The colour and/or style can indicate that the wearer of the sword belongs to a particular unit.

3. Rank insignia. The colour and/or style can indicate the military or government rank of the wearer.

4. A wrist strap to assist retention of the weapon in combat. Typically, the wrist strap is a loop which can pass through a hole in the hilt or a hole in the guard. Sometimes such a wrist strap is very plain, and at other times it can incorporate an ornamental tassel.

5. Magical or talismanic. For example, a tassel with a protective prayer. This can have important effects on combat, and should not dismissed as uninteresting superstition. In particular, if the wielder of a weapon with a protective talisman feels protected, their performance in combat will be less reduced by stress. See Hall, David Avalon Hall, Marishiten: Buddhism and the warrior Goddess, Ph.D. dissertation, University of California, Berkeley, 1990, and Serge Mol, Invisible armor: An Introduction to the Esoteric Dimension of Japan’s Classical Warrior Arts, Eibusha, 2008.

Some examples of sword tassels:

British, ornamental: https://collections.royalarmouries.org/object/rac-object-15055.html

British, military, ornamental: https://collections.royalarmouries.org/object/rac-object-32515.html The tassels on these basket-hilt swords have been explained as evolution from practical padding:

Late in the seventeenth century a short, thick woollen fringe, fitted inside the guard just below the pommel, was introduced - presumably to prevent chafing of the skin. As a probable consequence, it became the practice to leave the lower half of the pommel rough and unpolished, since it was almost entirely concealed by the fringe. This fringe was enlarged during the eighteenth century to the inordinate length it is now, and moved to outside the hilt.

• J. Wallace, Scottish Swords and Dirks: An Illustrated Reference Guide to Scottish Edged Weapons, Arms and Armour Press, London, 1970

Indian: https://collections.royalarmouries.org/object/rac-object-1702.html

Chinese (Qing, military): insignia and retention strap: https://commons.wikimedia.org/wiki/File:Baningga.jpg

Chinese (Qing, military): insignia and retention strap: https://commons.wikimedia.org/wiki/File:Arigun.jpg

British: insignia and retention strap: https://commons.wikimedia.org/wiki/File:Sword_and_scabbard_(AM_696820-7).jpg

British: insignia and retention strap: https://commons.wikimedia.org/wiki/File:Sword_(AM_696824-1).jpg

British: ornamental, and possibly insignia and retention: https://commons.wikimedia.org/wiki/File:Thinktank_Birmingham_-_object_1931S00162(1).jpg

Modern martial arts instructors and students will often claim other functional uses, such

• Distracting the opponent

• Helping balance the sword

• Provides visual feedback to the instructor and/or student that the technique is being performed properly during training

I have seen no good evidence that it is useful for distraction. While a tassel, especially a heavy one, does affect the balance of a sword, a tassel can move unpredictably and the effect can be undesirable.

The modern Chinese martial arts sword tassel appears to be a flamboyant evolution of traditional sword tassels - as seen in the Chinese examples above, these were usually modest in size, and functional as retention straps.

Spear tassels can perform the same tasks as sword tassels (except as retention strap, except in unusual cases). In addition, it is often claimed that they are useful for stopping blood from flowing onto the haft. Given that many fighting spears as used by ordinary soldiers lack tassels, this is not an important task. There are, in addition to the functions of sword tassels, three possible additional functions:

1. The tassel itself can reinforce the top of the haft - a binding around the end of the haft can help prevent splitting.

2. The tassel can be used to bind a crosspiece (wood, antler, metal) to the haft to help prevent over-penetration of a target. Such crosspieces were used on both hunting and military spears.

3. The tassel can help prevent water from entering the socket, by diverting rain - a little raincoat for the bottom of the socket.

Some spear tassels:

Indian: https://commons.wikimedia.org/wiki/File:Gouache_painting_on_mica_of_a_guard_or_officer_who_holds_a_spear_over_his_right_shoulder.jpg

Philippine: https://commons.wikimedia.org/wiki/File:Krieger_1926_Philippine_ethnic_weapons_Plate_6.png

European: https://commons.wikimedia.org/wiki/File:Vereenigde_Provincien_der_Nederlanden.(V-B-yiullsen).1660(NYPL_b14896507-91600).jpg

European: https://commons.wikimedia.org/wiki/File:Drabantspjut_från_Pommern_-Skoklosters_slott-_31013.tif

European: https://collections.royalarmouries.org/object/rac-object-24189.html

European: https://collections.royalarmouries.org/object/rac-object-14866.html

Afghan: https://collections.royalarmouries.org/object/rac-object-44462.html

Canadian: http://www.rcmpveteransvancouver.com/ric-halls-rcmp-lance-pennon/

Some Chinese military tassels (and cross-pieces to prevent over-penetration) can be seen at http://mandarinmansion.com/spears-qing-dynasty - note that some of the spears have no tassels. One example of a Chinese officer with a non-tassel spear: https://commons.wikimedia.org/wiki/File:Ayusi.jpg