It really depressed me at the time, realising there was a class of entrepreneurs and backers who were genuinely stop-at-nothing, even if it meant their three-year-old at day care was wondering why he was the only nappy-wearer, and carrying that subliminally into later life.
What I learnt from that and host of other experiences over time was that a young family and running a venture-backed, high-growth trajectory business aren't very compatible, but...
What I've also learned is that your first venture's going to be imperfectly executed anyway, so get the learnings out of the way anyway, with kids in the picture, then go again when the kids are school-age, and hope they get to enjoy the fruits of venture number two as teenagers.
Also, I never saw consistency from the people who put venture before family. They'd be buying shots for young staff at 11.00 at night on a week night, checking their crypto-balance continously, micro-managing, taking unnecessary business trips, etc. There are some absolute time-management machines out there, who never seem to waste a moment of their working days (I know two, and they both combined successful startups and young families), but in reality everyone needs some downtime/respite and family time is a better restorative than anything else except pure rest.
On that point, there's the famous adage, 'Startup, sleep, parenthood. Pick any two.' I picked startup and parenthood. Sleep deprivation means I look 10 years older than I am, but no regrets.
Finally, I think kids give you a second wave of competitive determination after your initial ambition wanes. Problematic investors, cheating competitors, over-demanding enterprise customers, careless execs, etc. could leave a lone individual feeling sorry for themselves, and defeatist. It's amazing how creative and determined one becomes when it feels like these different personas are causing setbacks that, rathervthan just interfering with your personal ambitions, might be stealing your kids' future opportunities and financial security.