Why do the Japanese love tanka?

The tanka is a uniquely Japanese poetic form perfected in the beeinnins of the seventh century.
Its original form can be seen in the Manyoshu an anthology of poems compiled in the eighth century.
Words which express the poet's feelings or the seasonal conditions are set in a 5－7－5－7－7 syllabic structure.
With no "season words" as required in haiku, tanka allows more freedom of subject matter.

Tokai no / kojima no iso no / shirasuna ni
(On the white sand of a rocky beach on a small island off the Tokai coast)
Ware nakinuret / kani to tawamuru
(Soaked in tears, I play with a crab)

This is a poem by Ishikawa Takuboku (1886-1912).
If you read it aloud, you will hear the 5-7-5-7-7 rhythm.
The pleasing resonance of the words is one of the reasons Japanese have long cherished the tanka.