Friends aren't important to everyone.
I understand the logic. Don't only have your husband in your life incase the marriage goes tits up. It's sensible. However not always practical.
Also friendships can go tits up. As you know.
The friend I mentioned before, is a friendship that's come about without trying. Neither of us were actually looking for a new friend. Or even that fussed. But it occurred naturally.
Also people are all different, friendships mean different things to all people. And sometimes people's lives move in different directions which mean you move away from each other. The more people you meet and get to know the more difference you see.
I may very well regret not fostering better friendships if my dh left me. However we have had a good 15 years together so far. We share a house and kids and a life. It makes sense to spend more time focusing on the person i want to spend time with.
I am fully aware that it could go horribly wrong and I may regret it. But right now, it makes me happy. Dh is the same (which helps) one good friend, who travels the world so don't see him that often. But if dh got tickets to a gig or an event, I would be the person he wanted to go with.
For both of friendships come second to our marriage. Luckily our two good friends are the same. Which is why it works.
Sorry I am babbling, worrying I am not explaining myself well. 