Most cups, which the Western people use every day, have a handle.
However, the Japanese one hasn't.
Why?
I, Masato Niitsu, a National Tour Guide, will explain details.
When the Japanese drink a delicious Japanese tea, they pour the right temperature tea to the cup.
So the Japanese teacup needn't a handle.
If the cup filled with Japanese tea is too hot to hold, you have to wait until you can hold it.