Actual quoting aside, do you use quotation marks to indicate emphasis, or to indicate fatuousness?

This is something that has always bugged me a little. For example, when I see a sign for “fresh” tomatoes, I read it as though just the opposite is true. Kind of like they’re being tongue-in-cheek. However, what what they actually mean is to convey is that the tomatoes are indeed “fresh.”

It’s no biggie, but it always throws me off! If they want to emphasize, why don’t they just cap it, or underline it or something? Why the quotes?