In my experience friendships can only endure with either significant history or because its mutually convenient to, with neither of these things you're more than likely going to drift apart
^^ This!
Friendships deepen when you have things in common or are going through similar life experiences.
I have limited time and energy to meet friends childfree so I save this precious time for friends I really like, friends I have a long shared history and lots in common with.
When I had DC I let a couple of friendships drift. One of my childfree friends met up with us a few times. I tried to make it as pleasant as possible for her but that’s not easy with a toddler. We went to the beach, toddler wanted to build sandcastles and babble, friend wanted my exclusive attention. Then friend decided to swim and wanted me to take photos of her, but I couldn’t get the perfect shot as I was watching toddler. Then toddler got hot and grumpy so we had to leave the beach early.
When toddler had her nap friend took the opportunity to talk endlessly (uninterrupted) about her DH problems, her cats, her new diet, her gym schedule. I listened but struggled to stay awake. It was like we were worlds away from each other.
Friend also showed no interest in my DD, fair enough but nor was I interested in seeing photos of her cats, holidays, ice climbing or faking delight at tales of her job promotion. I listened politely to these monologues but realised we had little left in common.
When DD woke up friend was grumpy because she wanted to go out for tapas and I needed to get DD home as she was whining and overtired. I invited friend to come with us and she did, but she made it clear she was annoyed at DD being centre of attention.
When DH came home friend didn’t understand why he couldn’t take over so we could ‘go out for drinks’. I tried to explain he could but I was shattered and DD would wake at least twice then start the day at 5am (or 4am if I was unlucky!) Nagging an exhausted mum of a toddler to go to a bar is a swift way to cool a friendship. I expected a bit of compassion from her.
Pre kids I would have found it annoying too but when you have one your world revolves around their needs for a few years. Socialising in bars is the last thing someone wants to do when sleep deprived and struggling with PND.