Contractions in essays

Hi, most of the ESL essay guides say not to use contractions. I was checking an essay today that included:

"So why do not you join our club? "

This sounds very unnatural to me, but

“So why don’t you join our club?”

Sounds quite natural. Do you think ESL test takers should always follow the “no contraction” rule?

Contractions are essentially informal and to read them in a formal essay does tend to jar. Going back to the days when I was an assistant examiner for the Cambridge Proficiency, I would certainly have marked contractions
down in the formal essay part of the exam. I think you could easily get round your example by writing: Why not join our club?

Alan

Hi Alan,

please explain why you used “Why not join our club?” and not “Why not to join our club?”
Is it possible to use infinitive instead of the bare form you used in the sentence.
If it is better to use bare infinitive in such sentences, please let me know why!

In addition, is “Why not join our club?” a short form of Why don’t you join our club?"
If so, isn’t “Why not join our club?” informal way of saying as well?

Thanks

The infinitive ‘to join’ is not correct in the sentence ‘Why not join our club?’ because as you say ‘the full form’, without assumptions would be ‘Why do you not (don’t you) join our club’. The tense needed has to match ‘You’. ‘You join…’ ‘I join…’ ‘We join…’, ‘They join…’

As you can see from my last sentence, the full form is ‘Why do you not join our club’. I don’t understand the point you are making in your final comment.