Most people don't know what a URL is, and you want them to install an OS ?
No. But I think the people who know how to install a windows can also install ubuntu.
Yes, many people I know would get stuck on the very first step: formatting and creating the bootable USB drive.
Canonical needs to put USB drives with Ubuntu into retail stores then :D
Aren't there apps to do that for you nowadays? :-D
Yeah, you need to google for a tutorial, install something like Rufus or unetbootin. Have the whole mental model about what iso files are what is a boot disk, how to fix the boot order in bios if needed, etc... Very far from trivial for most people.