Men can develop deep friendships with each other as adults, it "just" takes enough mutual interest and flexibility to spend a lot of time together. That is much harder if your time is already spoken for my family, a partner, children, work, hobbies, etc. Think of all those sitcom friends who just show up at each others' houses and hang out.

Friendship is fundamentally when two people want to spend time talking with each other (without an ulterior motive like sex or commerce).