Some of it are the expectations that are placed by the organisations like schools. My DD wasn't allowed to leave by school unless an adult was there, at the door, to collect her. Even in her last year of junior school, when she would be fully expected 6 weeks later to leave the house and get on a school bus and be dropped off by the same bus in the village and walk home independently from there.
I've promoted independence, partly because I had to but partly because I had to learn to be independent without a safety net to catch me if I screwed up.
I've tried to promote the independence but provide the safety net for the inevitable mistakes that will happen as children and adolescents learn to become adults. I felt some of this was undermined by other people, such as the school when it came to things like asking me to 'pop' some forgotten homework in or PE kit - if I wasn't actually doing anything at the time, then I would, because I like to help my DD. Other times I said no, because it meant me taking the concequences of her mistake, and I felt it important that she face those concequences and deal with them to learn that you're responsible for yourself. The school took a dim view of this at times, insisting that I should walk out of work (which by law I couldn't do anyway without cover) and make an hour's round trip to prevent my DD being sanctioned in some way for forgetting her homework or PE kit.
I would remind her the night before or that morning to ensure she had everything she needed for the school day, more than once, but ultimately she needed to learn that she's responsible for herself.
As for illness or injury, I wasn't particularly bothered if she scraped her knees, or grazed her hands, I taught her to self evaluate and treat when she hurt herself and seek help if she needed it, so she was quite capable by 6 or so of washing off a graze and applying a plaster herself. If she felt unwell, I'd take her temp, look at her general demeanor and make a decision from there, she does the same now. If she doesn't feel well enough to go to college, I trust that she isn't well enough. I provided comfort, yes it does hurt and that sucks, a little cuddle and some kind words, but then off you go again because it's not serious and it won't stop you doing anything. I don't subscribe to the 'well I had to and it didn't harm me therefore you do too' school of thought, but rather offer empathy and understanding and an explanation. Falling over hurts, but you can evaluate the situation yourself and deal with it yourself unless it's more serious in which case you need some help, which is provided without question. The knack was teaching the difference between the two.
I think as she's grown, this approach has served her well, and as a new adult, I encourage her to be independent and try things herself first and I will provide support and help when needed. She learned the importance of being organised and prepared, has got herself a job (delayed by covid admittedly) independently and manages it all herself, has managed organising college herself and catching up, organising extra tuition etc where it's been needed - with my guidance and at times intervention, but mainly by herself.
She's doing her university applications independently, I have researched it myself, know what's required and am on hand to discuss and guide where needed, but I'm keen she does it herself rather than letting me organise her life for her.
She's got to find her own way in life and I'm her back up.