Would it kill you to say hello?

 I'm not really a people person and never have been. But I do at least have a modicum of courtesy. Say hello and I will say hello back. Alright, I might then run out of things to say and if you set off my Nutter Radar you might find yourself speaking to somebody edging away in indecent haste, but I will make the effort to be pleasant. .
 In a similiar vein, if you're somebody I start seeing around on a regular basis - a co-worker, neighbour, guy I buy my kebabs from - then I'm going to start saying hello to you. Common courtesy, as far as I'm concerned. And most people will nod back at a minimum. There's no great effort involved and it makes life slide by a little easier.
  So it irks me somewhat when the other person blanks me totally. Or -and I've had this done to me - gives me a quick once over to decide whether I'm worth speaking to then blanks me.
 The obvious question is: Are you that far up yourself that you cannot spare a few seconds of courtesy?  Or are you afraid that saying good morning is some sort of binding commitment?
 I suppose you are doing me a favour. Because you've just let me know that, really, you're not worth my time and effort either.