This probably sounds like a silly question, but house flies (not biting flies that are trying to get a meal or mosquitos that need blood) repeatedly land on me until I get sufficiently annoyed to kill one. Then I am usually not bothered for a number of minutes until another one takes it into his tiny brain to start bugging me. And if he is sufficiently annoying I will dispatch him too. You would think that unless there was some evolutionay advantage in landing on me, eventually flies would stop bugging us. More precisely, flies that kept away from himans would have a selective advantage and win the evolutionary race over the others.
There’s a reason they’re called “bugs,” ya know.
The titles gives the perfect set-up. That’s the best you could do?
OK, OK.
- Maybe you should stop using fertilizer as aftershave?
- Try taking a bath once in a while.
- Lay off the insect-pheremone cologne?
- When a person comments that you may be falling ill, don’t respond, “No! I’m getting BETTER!” in a raspy voice.
OK, I got nothing.
I’ve been meaning to ask the same thing as the OP. Why do they feel a need to land on me and buzz around me? They do not take a bite out of me and if they are looking for something to eat wouldn’t it be easier for them to just flyy to the kitchen counter or something where there’s probably all sorts of goodies for them to eat.
Why can’t they understand that bugging me only leads to a fatal encounter with the flyswatter? 
Perhaps they are seeking the moisture and/or salt that your skin exudes via perspiration?
It’s always intrigued me too I must say. Here in Aus, especially when on camping trips in the middle of nowhere and with no other human within coo-ee, I have always been fascinated by the number of flies that can find their way to my face, neck and any other exposed part of my bod. What the hell do they do for fun/gratification when I’m NOT here? 
This is my experience too. Flies won’t stop buggin’ me whenever I am all sweaty and they totally ignore me when dry.
It seems the consensus around here that houseflies go for the hair. I really don’t get that.