Wow. Everyone single here has pretty much nailed it. So called free pussy is such a damn hassle, man. Almost not even worth the effort sometimes.
With providers, you can get someone really mouthwatering hot. Not so much with civvies. If you're good enough to pull it off and bang somebody who I've seen LOOKS like she should be a provider, more power to you. But those kind know they're super hot and will make you swim through lava to bang them (meanwhile, they're letting the kind of guys slim described hit it with almost no effort on his part at all).
Providers = path of least resistance, and usually with no drama to follow.
Easy math.