Exactly this. You do tend to get the 'I'm 54 with an 8 year old and I am super fit and never tired and am coping fine' type posts on threads like this, but to be honest, they are coping because they have to, as they have no choice. And even if they are struggling and regretting having a baby at 44/infant age child at 50/teenager at 60, most people won't admit it.
As has been said, many people feel fit and healthy and still feel 'young' in their early to mid 40s, but it's not long after this that most people will start to go downhill health wise, and feel their energy zapped out of them.
By 50 many people will start to have health issues, and as has been said, will be winding down and wanting to relax by 55, not be running around after young children. Measurable physical and cellular health declines often become more noticeable around age 50,
Bone density and muscle mass start dropping faster, which increases the risk of weakness or fractures if not actively managed.
Physical tests show that balance and core stability often begin a noticeable downward trend right around age 50.
Hearing and near-vision changes frequently become more pronounced during this decade.
Menopause typically occurs around age 51, bringing shifts in oestrogen, sleep patterns, and bone health.
Research points to the 40s and 50s as a period of distinct molecular shifts affecting lipids, skin, and cardiovascular function
And as a pp said, ( @OneLilacHedgehog ) the 50s is the decade where many people have died of cancer. I have personally known many people die in their 50s of cancer over the past 5 to 10 years. (And most people I know have known people die of cancer in their 50s, and a few in their 40s...) And as that same poster said, the vast majority of people are not excited to still be working at 58. Most people would give their left arm to be retired by then! Very few people want to HAVE to work full time in their late 50s (and 60s) so they can afford their children.
Also, as was pointed out by a poster further back, @timberwolf79 (whose parents were middle aged when they had her/her father was in his 50s,) it's very unfair on the children too, to have pensioner aged parents when they're still in their teens, and to have to be caring for elderly parents who are ailing and frail, by the time they're in their early to mid 20s.
I am in my mid-late 50s, and my DC are in their mid-late 20s. (I had them around 31-32.) I cannot imagine being 15 years older, (in my early 70s,) and having children only in their late 20s. Many people start to need care by their early-mid 70s, and I can't imagine for one minute, expecting my young 20-something DC who have their own life, home, careers, friends, social life, and hobbies and interests, to be waiting on me, looking after me, running me around, and doing shopping and housework for me.
Yes, I know some people in their early-mid 70s are fine, and can look after themselves, but statistically, many people will need help and care by their early-mid 70s. Around 1 in 5 people in their mid 70s require regular assistance with daily living.
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