By western you mean America? Cause this is true only in America.
And to add salt to the wound, it's the people on the positive side of the economic bell curve that have strong familial support networks where grandparents and uncles and aunts can contribute to childrearing, while those on the other side of the curve can't always rely on having those support networks. A generalisation of course, but a relevant one.
The first 6 weeks: 90% of average weekly earnings
The remaining 33 weeks: £187.18 or 90% of average weekly earnings (whichever is lower)
So not much after the first 6 weeks
Some data for non-statuary maternity pay https://www.incomesdataresearch.co.uk/resources/insights/mat...
Later
From the people I know, the financial pressure seems to build around 6 months as their employer's maternity pay is fading into the distance, but they struggle on a bit longer.
I admit there may be different definitions of "as soon as possible" between the USA and other countries. Most people here would love to be able to afford at least 1 year if not more.
Just because the the US provides zero paid leave by law doesn't mean women don't take maternity leave - it's often self funded of course. How about you look into that and compare, instead of trying to ask specific questions to arrive at a gotcha