Greeting people is such a waste of time

One of my colleagues confronted me because I'm apparently rude and unfriendly. Her issue is that I don't greet her every time I see her.

I honestly try to remember to, but I don't see the point in it so I often just forget. Unless I want to have a conversation with someone, I don't see the point in randomly greeting someone.

It's one of those social things I just don't get which makes it harder for me to remember to do it. I don't want to come off as rude. It was just a crap confrontation and it's really demotivating because I really try