I think the reason a lot of men who are stuck in this mindset stay stuck in it is because the only time they actually do think they can be vulnerable is when expressing love to their partner. So it's something they crave and don't realize they can be vulnerable in other contexts. I think it's part of what leads to red pill mentality.
It's hard for men to understand how patriarchy also hurts them. It expects men to be stoic protectors. Emotional vulnerability is a sign of weakness under that worldview.