or is it just me?

Started a new job a little while ago and have begun to notice the lengths people will go to avoid a conversation with a colleague they barely know. Taking the stairs when they were clearly going to use the lift etc.

I've never really understood this - what's the harm in just having a little natter (even if it is just small talk about your weekend/how shite the lifts are/the weather) and then getting on with the rest of your life? Anyone...?