It's why day care, head start, school lunch and the like are super important.
Even before we get to corporate demographics or college graduation, admittance, and application rates, there are millions of children growing up in poverty in the US. Relatively inexpensive social welfare investments can mitigate many of the worst effects, even for those who don't decide to become software engineers.
None of this matters if the children grow up in a single-parent household. Keeping a two parent household has an outsized influence on the children's development and needs to be a cultural shift in our society.
"single parent households" are precisely why these levers are important: among other things, they help reduce the disadvantages some kids have due to being raised by an impoverished single parent, and gives those kids a leg up in a way which will foster more stable home life and less likelihood of themselves becoming single parents.
Not only that, but more resources and more stability help foster successful relationships. If you want more two-parent households, make it a lot easier to have and care for a child.
It can absolutely matter, and in fact it is all the more important in a single-parent household.
You’re right that single vs. two parent household is the largest contributing factor. You’re wrong that it means that no other factors matter at all.