I wouldn't call them a crutch at all. Many a time have I used the
:-P emoticon to convey sarcasm/jest, or the
=) smiley to illustrate that I am smiling in merriment or happiness as I make a statement.
So what if authors have been writing clear sentences withough smileys for years? They have the liberty of writing statments such as:
"Oh, right... you're gonna climb Mt. Everest tomorrow," Jack said incredulously.
They have the ability to tack extra modifiers onto a sentence that don't actually come across in spoken language to convey the extra emotion.
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Also, in today's world of short attention spans and
Internet time, smileys/emoticons save a lot of time when trying to convey feelings/emotions. A simple :-) as a replacement for "Hey, that's pretty cool!" is quite desirable, in my
opinion.