The other day, I was getting onto the subway, coming back home after a long series of classes. I saw a friend of mine, and he was busy with his phone, so I quietly sat down next to him and pulled out a book.
I noticed he was playing a game of some kind and seemed pretty absorbed, so I quietly went back to reading. We sat there silently ignoring each other for most of the trip. It wasn't until just a couple stops from mine that he noticed me, said hello, apologized for not noticing sooner (which I didn't think was necessary) and we had a great conversation the rest of the way back.
Fascinatingly enough, later that evening I went to my Shul to sort out the whole selling-my-chametz business. I sat down with the form trying to figure out what I had, where it all is and how much it's worth when I realized that I'd been sitting for several minutes next to a good friend without even noticing!
We men (perhaps it's more than just us men, feel free to chime in with your input/experience, ladies!), we're fascinating like that. If we're focused on something -could be trivial as some game on our phone we only play on the way home to pass the time or very important like making sure we're not violating a Torah prohibition -we become fully absorbed in it and really don't realize what's going on outside of that focus. It's like the rest of the world does not exist for us.
It has nothing to do with importance or how much we care. I know my friends love me and I love them dearly. But when focused on something, we'll screen out pretty much everything that isn't relevant to the task at hand (or the object/person we are focusing on).
None of it has to do with offense or intent. But also, as men, when we are focused on something it is actually quite frustrating to be snapped away from that. It can even be a painful experience, to forcefully take our attention away from our focus (think about trying to get a guy's attention when he's at a sports-game) and the result -if we are not handled with care -may be a grumpy, angry or frustrated response. It's for this reason (among others) that we often resist having our focus (unwillingly) drawn away from the task, object or person in front of us.