My current hospital is a small secondary one. There are no obstetricians or anaesthetists or paediatricians after hours or on weekends, so if you have an emergency the team has to be called home and wait.
When I was working at a tertiary hospital often the theatres would be busy. I once had to wait 2 hours wirth a woman haemorrhaging before being admitted to OT. The midwives were the ones tasked with keeping her stable until OT was ready.
So no, necessary emergency help is not always immediately accessible at hospital. In one of the last home births I attended, the woman had a postpartum haemorrhage which myself and the second midwife managed. That woman was at the hospital in 40 minutes where they only neeed to monitor her, as we had stopped the hemorrhage and administered all the emergency drugs before arrival. The woman was really happy that she had had a home birth and the hemorrhage and ambulance transfer was just part of the care she expected from her homebirth midwives if things didn't go to plan. All HB midwives are prepared for this and can stabilise a woman and/or newborn for transfer if necessary.
Sometimes I cover remote rural areas where a hospital is over 3 hours away. Transfer may involve a helicopter rescue (which I am also certified to do). In these areas, my threshold for intervention/transfer is obviously much lower than when I am working in hospital. This is part of the hierarchy of decisions midwives and women make as part of their very individualised care and experiences.
Each woman and baby will have a different risk background and we have these discussions with them during the whole antenatal period. Midwives and obstetricians can discuss the obstetric risk with them, however the women have other risks and other factors which affect their decisions, not exclusively medical risk.
When you plan a hike in the wilderness, a skiing trip or a holiday abroad, you also consider the medical risks (you can fall and break a leg, hit a tree, your rental car can crash...) and try to mitigate them. But the final decisions will involve many more factors than medical risk only. If you only considered medical risk in your life decisions you would spend your life stuck at home and living in a flat close to the hospital just in case... in summary... you wouldn't have a worthwhile life.
The same applies to the decision about place of birth: for many families the decision to birth at home or hospital includes medical risk, but there are plenty of other factors in their individual lives which may be equally important, or even more important, than a relatively small medical risk. A risk of 1 in 500 can be very small for some people and very large for others.
Do you know what's the highest risk factor for maternal death in the UK and most of developed countries?
It's not hemorrhage, it's not infection, it's not any of the labour and birth risks you may be thinking about.
It's suicide.
All the "safety" you imagine you have in hospital will be for nothing if the woman ends up killing herself after her labour experience due to a traumatic birth or a consequent postnatal depression.
So before telling others what they should do about such an important even as their birth, please consider that other women's lives are not like yours, and their reasons to make decisions you would consider "risky" as are valid as yours to birth in hospital.