Why would font names need quotes?

Question

As far as I know, one needs to use double and single quotes for the fonts if they contain space like:-
font-family: "Times New Roman", Times;

But on Google fonts(https://fonts.google.com/), I also see
font-family: 'Rubik', sans-serif;

Some even use it like so:
font-family: 'Margarine', 'Helvetica', arial;

I find this weird, as the following works as well:
font-family: Margarine, Helvetica, arial;
font-family: Cambria, serif;

So what is the correct usage of quotes around font name in CSS?

Answer 1

Quotes are used for fonts that have spaces in their name - that are more than one word. For single-word fonts, you don’t have to put quotes, but you can if you want - entirely your decision.