I'm Canadian, and I say "folks". However, I usually tend to say it to sound different from others. I like the sound of the word, even though it's something mostly older people say. When I personally use it, I usually refer to my parents.
It's often used in familiar company, or used to address people in a friendly, informal way. Hazel and Parker both have good answers. Folks is meant to be used in a familial setting to sound jolly and informal. It's meant to be inviting, so the speaker seems to be on a friendly term with you. It's also a little dated, so I often hear mostly older people use it.
In my family I have heard:
"You folks have better weather out here than we do." (folks = family members)
"I told my folks about that." (folks = parents)
From non-family members, I have heard:
"Step aside, folks, the line forms on the left." (folks = people)
"What can I get you folks?" (you folks = people)