Most people know the basic rules for quotation marks. You use them to set off dialogue in a story, or to capture the exact words of someone in an article/interview. There are single quotes and double quotes, with U.S. rules being to put single quotes inside doubles, and the opposite for the U.K. After that, it gets a bit hairy for most people. However, the general consensus now is that quotation marks should be used for directly stated material, and italics should be used for everything else as much as possible. That includes, emphasis, sarcasm, and words as terms. By using italics in place of quotations in these instances, one can avoid scare quotes. Scare quotes are quotations used as a means of emphasizing or giving a sarcastic tone to a term or phrase. For example, in the sentence, "The politician droned on about the 'importance' of welfare," the word importance has a clear, sarcastic undertone to it, illustrated by the use of quotation marks around it. However, you can see how annoying these extra marks might be, especially when an article is littered with them. Political statements are notorious for such blunders and can be quite frustrating to peruse as a result.
Yet, there times when quotation marks make more sense than italics or simply look better. As you probably noticed, I used quotations when highlighting the example sentence in the previous paragraph. The material was neither a direct quote, nor was it a vocabulary term. However, since I was referring to a specific statement lengthier than your average word or phrase, it made more sense and was more aesthetically pleasing to set off the material using quotations rather than italics. When I then mentioned a single specific term after it, I chose italics.
From a stylistic standpoint, a mixture of quotations and italics is rather useful. But as with most of the standard English rules we've adopted, the grammatical criteria tends to be somewhat fluid. The U.S. is one of the few major countries that does not govern over its official language. Many countries actually have a council dedicated to monitoring and processing changes. In some ways, that makes learning the rules easier. Everything is more concrete, and there's little question what is right or wrong. Yet, I would argue the beauty of the English language is the fact that it can morph rather easily. Without that flexibility, the digital age, for example, would have done a number on the English language. Instead, it adapted, creating new words that were almost immediately recognized and accepted, prompting other countries to adopt our vocabulary for ideas such as the Internet, World Wide Web, and email.
Still, there are times when having a critical eye for unpleasant punctuation is necessary. Particularly true of non-fiction, scare quotes are seen as somewhat unprofessional and certainly extraneous. By the same token, one can overuse italics when replacing scare quotes. The best policy is to use both sparingly and only when appropriate for clarification or grammatical accuracy.
In case you're skeptical of the effect scare quotes have, here are some hilarious instances of what I'd like to call "scare quote overdrive." And yes, you can quote me on that.
Other references: http://www.quickanddirtytips.com/education/grammar/single-quotation-marks-versus-double-quotation-marks https://owl.english.purdue.edu/owl/owlprint/577/ The Grammar Grind: Quotation Marks