Holy shit at the amount of nasty replies to a simple enough question.

To answer OP, as some people have already said I don't think society makes it as much a concern as it does things like shaving your legs. And sure, some women choose to not shave anything.

I also don't believe that all women think to do it, again maybe that is because of society and whatnot. Unless you have very dark hair and it stands out I don't think a lot of people would think to try it.

I will admit I do it and it's a quick thing for me to take care of daily. I'd guess under a minute. It isn't time consuming and I never have stubble like I do my legs. I hate shaving my legs, it's a much bigger PITA to me.

I honestly had noticed that a friend had done it which made me start considering it. This was way back in high school, ten years ago. She had very very dark hair. It looked better, IMO. I began taking note of what other women do. Most people didn't have shaved arms that I saw so I thought my friend was just on to a good idea, with having dark hair to blame. My hair is a lighter brown but on my arms it was very dark looking and noticeable. I gave shaving a shot and have stuck with it ever since.