Why should you learn to punctuate properly? After all, many people have made successful careers without ever learning the difference between a colon and a semicolon. Perhaps you consider punctuation to be an inconsequential bit of decoration, not worth spending your valuable time on. Or perhaps you even regard punctuation as a deeply personal matter — a mode of self-expression not unlike your taste in clothes or music.
Well, punctuation is one aspect of written English. How do you feel about other aspects of written English? Would you happily write pair when you mean pear, because you think the first is a nicer spelling? Would you, in an essay, write Einstein were a right clever lad, 'e were, just because that's the way people speak where you come from? Would you consider it acceptable to write proceed when you mean precede, or vice versa, because you've never understood the difference between them? Probably not — at least, I hope not.
Yet it is quite possible that you do things that are every bit as strange and bewildering when you punctuate your writing. Perhaps you use commas in what we shall soon see are surprising places, merely because you think you might pause there in speech. Perhaps you use semicolons where you should be using colons, because you've never quite understood the difference between them. Or perhaps, if you're really committed to punctuation as self-expression, you just stick in whatever punctuation takes your fancy, because it's your piece of work, and so it ought to have yourpunctuation.
The problem with poor punctuation is that it makes life difficult for the reader who needs to read what you've written. That reader shouldn't have to make allowances for your personal tastes in spelling and grammar: she expects to see standard English spellings and standard English grammatical forms. And the same is true for punctuation: she is most unlikely to know what your personal theories of punctuation are, and she won't be interested in them. She'll only be interested in understanding what you've written, and she's going to have trouble understanding it if it's badly punctuated.
When we speak English, we have all sorts of things we can use to make our meaning clear: stress, intonation, rhythm, pauses — even, if all else fails, repeating what we've said. When we write, however, we can't use any of these devices, and the work that they do in speech must be almost entirely handled by punctuation. Consequently, written English has developed a conventional system of punctuation which is consistent and sensible: every punctuation mark has one or more particular jobs to do, and every one should be used always and only to do those jobs. If your reader has to wade through your strange punctuation, she will have trouble following your meaning; at worst, she may be genuinely unable to understand what you've written. If you think I'm exaggerating, consider the following string of words, and try to decide what it's supposed to mean:
Bad punctuation does not require an enormous effort to put right. If you work carefully through this document, then, providing you think carefully about what you're writing as you write it, you will undoubtedly find that your punctuation has improved a great deal. Your readers will thank you for it ever after.