My Adult DD lives with me, she was managing it until the driving lessons started.
She does sometimes put 10% away, but to do that consistently she wouldn't have any sort of social life and I'm not talking big nights out. She will have Student debt.
My middle DD (two young children) can't. She can save up for the summer holidays starting now, then Christmas, but is playing catch up.
My eldest does, but house repairs and then her holidays take nearly all of it. She had to buy a fixer upper to get on the housing ladder.
I tend to need something in sight. I've got a savings account for a holiday I want in nearly two years. I have about £800 for a replacement appliance, separately.
"When the mortgage is repaid we will easily be able to do it, but that is not for another 28 years."
I'm mortgage free, but I'll need a new kitchen and bathroom within five years, so whilst you do save money, of course, you need to calculate your borrowing in regards to retirement etc.
You are never fully sorted unless you are an above a middle earner and your children manage the same. I'm having to help out my DD with her children, she's a LP and has been hit hard by UC. Whilst part supporting my youngest. Brexit and Austerity is destroying our City and employment.
Being a Carer for my Mum, meant I couldn't take on extra hours, she died three years ago.
I know lots of people financially helping out family.
It is partly a matter of luck, or a stuff everyone else attitude.