Can anyone explain why you have less/no razor burn with a straight vs any other tool?

As I'm a newb, I'm scraping like a mad one over certain spots of my face (old habits die hard) and still I do not have a single spot of razor burn. My neck used to get chili pepper red when I shaved with a mach3 for example (with quattro it was just nightmare). With a DE I also get almost no razor burn. My question is simply, why? How come? I don't get it, the way I'm shaving with the straight, I' pretty sure my face should be on fire, I mean I'm craping a knife over my face