And if you're not close to your mum (or she's dead) and only have a brother ...
I don't have any female friends who would be in a position to leave work at a random point in a 6 week window to support me in hospital, and most of the ones who would be any good have their own children to care for ...
No one had overnight partners staying for either of my births, there was still plenty of snoring, screaming babies, rustling of food packets and loud phone conversations and videos.
All the embarrassing medical stuff was during the day when partners (and other visitors) were allowed. When I was induced I was on an antenatal bay, I was very close to giving birth with a whole family in the next bay, chairs against my curtain, they certainly got the benefit of my swearing while the midwives did the inducing gel stuff and when they checked how far I'd got - lots of scar tissue from first birth made the vaginal exams really painful.
If DH hadn't been there I'd probably have given birth on that bay, as he had to go fetch the midwife when I did my usual trick of 3cm to 8+cm in 30 minutes ... In the middle of dinner service.
I was at Telford Hospital when the baby death scandal was under investigation, the biggest impact at that point was the the senior MW (who I'd been randomly assigned) also had to show multiple bigwigs around the ward and show them what was happening instead of/as well as doing her job.
Until staffing levels are sorted women need advocates who aren't in pain and are mobile, and a very large number of women don't have female relatives who would be of any use to them at that point.
Also, if there's urgent clinical decisions to be made, better there is a next of kin/parent to make the big decisions rather than whichever female friend wasn't working on the crucial day!