Proximity effect is a tool that good vocalists *use*, and a trap that bad vocalists walk into. A lot of not-so-good rock vocalists, and many bad rappers spend their whole life with their lips stuck onto a dynamic mic. Usually, they learned this in $100 dance bands, where the PA and the sound man (if any) sucked so much that they had to do that so they could turn down the volume to reduce feedback. It also partially blocks access to the diaphragm for sound waves coming from other sources, particularly the columns/monitors, etc.
Then these Nimrods hit the big time, and continued their bad habits with perfectly good PA's and sound men. Really good vocalists learn where the proximity field starts on any given mic, and how abrupt it is. Some mics have a smooth, linear, progression of the proximity effect (SM7). Others, it is like a wall that you hit (AKG D3800 tripower). The really good singers brush the edge of the proximity field, moving in and out of it on purpose, for effect. The more abrupt the proximity field is, the more careful you have to be.
On stage, I try to project the illusion that I am singing to the audience (especially hot babes with big boobs), and make eye contact. I never forget, however, that my *real* audience is a 1" piece of gold-spluttered mylar, and I never forget where the proximity field is. It's like the difference between working the engine of a Harley or a Ninja. The Harley doesn't care that much what gear you are in, or what RPM range you are in. The Ninja has to be kept in its much narrower power band. The Ninja is faster, but busier, and less forgiving. My SM7 is my Ford F-150, and the tripower is my Viper with a 6-speed tranny.
Want to see a badass rock singer use proximity as a tool? Watch old films of Freddy Mercury with Queen. Want to see a clueless rock singer step into the dog do-do of proximity? Watch old films of Gwen Stefani with No Doubt.-Richie