Remember that alliteration is the repetition of sounds rather than letters.
For instance, crazy chickens repeats the letter C but is not alliterative.
The sounds are different.
When words alliterate, it creates a memorable sound, drawing the reader's attention. That is why advertisers use alliterative patterns, such as "Buy Barton's beef". Alliteration draws the eye and ear to emphasise a point or detail.
Forcing alliteration often creates more surprising and interesting word combinations. It helps the writer break free of the expected cliche, so rather than "the barking dog" you might write "the doubtful dog".
Of course, alliteration is sometimes onomatopoeic - "the busy bees"
recreates their buzzing. Young writers do not need to worry about onomatopoeia because if they choose powerful words, they may well be onomatopoeic
Pie Corbett is a literacy consultant