Read these three sentences:
There's a young lady here to see you.
There's a "young" lady here to see you.
There's a young "lady" here to see you.
You may also do this when speaking with the use of the 'finger quotes' hand signal, but some people consider this obnoxious.
However, quotation marks have never been used instead of a boldface font, all caps, or underline to emphasize a word or concept, as far as I know.
Oddly, I saw a lot of the latter in Las Vegas this weekend:
(first two from a restuarant menu:)
1) I thank the Lord for my "customers" and my family.
2) First order of chips and salsa are "free"!
(from a thrift store:)
3) Do "NOT" open bags!
Then today, back at work, I saw this at the now-closed coffee shop:
We have "soy" milk.
Which seems sinister, along the lines of something like:
We have "chicken" sandwiches.
Okay, off the soapbox. I sincerely "thank" you for your patience in listening to my rant's.*
*the rant about "'s" when a plural is meant rather than a possessive will perhaps come one day in the future.