Sometimes writers use quote marks to distance themselves from a word or phrase. They're treating the words as a virtual quote, as if they were saying, 'It's not really me using this phrase: I'm just quoting what other people say.'
Quote marks are difficult to handle correctly, goodness knows. But here's a tip that should be easy to follow. It's so simple: just don't do it!
Virtual quote marks imply something like this:
If the word or phrase in quote marks is genuinely unusual, and you are drawing attention to it as a word, that's fine.
If you habitually use virtual quote marks for the other reasons—beware! This habit can make the writer seem old-fashioned, naïve, insincere, silly or mean.
Always ask yourself whether that word or phrase is genuinely unusual. If not, quote marks may make you seem out of touch with today's common language.
Embarrassing use of virtual quotes:
Heaps of other tips like this in Modern Punctuation: a fun course, believe it or not!