I also don't understand why men don't constantly bump into each other if they're socialised not to give way.
They do give way to each other.
I started watching out for this after the coincidences of reading about it on MN a few years ago and being unable to enter a coffee shop in town because a man was standing in the doorway - filling the doorway - talking on his phone. He could see me. I was right in front of him. But he did not move.
I now no longer automatically or routinely give way to men. I haven't been bumped into but I have seen men jump out of the way to move at the last minute when they've realised I'm not going to move. I'd prefer a polite mutual sidestepping and when I notice them start to step aside, I do the the same.
It really brought it home to me in my local and I got sick of men 'moving' me out of the way with a hand on my shoulder or waist. So I decided to 'own the space' and stand my ground. The next time a man did it, I didn't move. He tried again and I didn't move. I don't mind being asked to move or if the guiding hand had come with an 'excuse me' - no, I'd have taken the guiding hand to be an indication of the direction the other person was approaching and wanted to move in. But I object to just being pushed out of the way. Anyway, on this occaision, the man stopped, looked around and said, "excuse me, mate" to the man standing next to me.
No, 'guiding hand' for him. No 'excuse me', for me.
I'm small but can walk quite assertively. Part of it's simply being aware, making eye contact if necessary. It's certainly not about being obstructive - actively giving way to people who need more consideration
I would agree with this. Since I stopped moving out of the way to 'be nice' and started 'owning my space' more assertively, I find it has largely stopped. And yes to not being obstructive.