Yep, people definitely scroll. Look at yourself when you're exploring a new site on your phone. Do you scroll to read more, or do you leave immediately?
The concept of "the fold" gets me every time, especially working with people who create lots of advertisements.
Sure, there are some situations where people go to a site, stay for 2 seconds, and leave immediately. But that's not because users don't know to scroll, it's because they're not interested in the content. Have you ever clicked on a link, just to be brought to a page you weren't expecting? You probably left immediately without scrolling.
But when people care about the content, they scroll. It's become a very natural gesture for mobile, just like how websites are usually viewed in Portrait more than Landscape. So don't worry about trying to get all your content above the fold. There's no way all that content is going to fit on a tiny screen (...except maybe on an iPhone 6 or 7 Plus).
The good news? This holds true for desktop as well. I see it all the time in Hotjar. Sure, it's pretty rare people for everyone to make it to your footer, but it's usually because they either have no interest in the content and leave, or because they've found what they're looking for and have gone to another page.
The key takeaway is this. Don't be scared of making your users scroll. Just make sure the content you want them to see really stands out. Give them a reason to scroll.