Sometimes it is in order to avoid using crass language.
For R. Joshua b. Levi said: one should not utter a gross expression with his mouth, for lo! the Writ employs a circumlocution of eight letters rather than utter a gross expression, for it is said, of every clean beast . . . and of the beasts that are not clean. (Gen. 7:2)
Instead of using one word (tamei – “unclean”) the Torah bothers to use three words (asher lo tahorah he - “which are not clean”) using eight letter more. Why? In order to avoid using the word “unclean.”
Other examples are given in which the Torah uses nine, ten and even sixteen extra letters in order to avoid an unmentionable.
The School of R. Ishmael taught: one should always discourse in decent language.
and it is said, and thou shalt choose the tongue of the subtle; (Job 15:5)
and it is said, and that which my lips know they shall speak purely. (Job 33:3)
Both texts from Job are brought in order to show that it is not only in sacred matters but at all times one should speak with dignity and refined language – avoiding cursing or crude words. Even if it takes a little longer.