I need some formalized experience document, even if your resume just looks like bullet points. It gives me discrete items/events/projects/education/skills that I can consider and discuss with you. If I don't have that as a reference point when talking with you, all I can say is "So, tell me why you're awesome", which is not useful.
If I'm not starting out with some idea of what we can drill down into, some table of contents, I have too little to work with and I'm not going to bother. Perhaps more relevantly, HR probably won't even bring you to my attention.