They can?
The reasons why Orcs rarely have children among themselfes is because those tend to challange their own fathers to a duel to the death... and considering the rarety of females in their own kind leads to constant struggle in between the strongest.
Only the weaker ones that realised they would never stand a chance against their leader would fall in line silently...cause a shift in that power struggle and chaos is ensured
Being rare in a 70% males 30% females, doesnt mean they cant have children or we don't see children.
Children tending to challenge others or challenge his own father to ascend in the social hierarchy is a common thing on those who move in hordes and tends to live on their own instincts.
On wolves they have a alpha male and female, the others submits, if they dont submit, they die. The alphas are always in fights to control the hierarchy, and even between those who are not alphas show their own position being aggressive and having fights.
On cows and bulls have the same system.
And if we go on other fantasy universes. Those who have a genre being unique, or 1/1000000 between 1000 years. Those are often those who rule over.
For example, in the Zelda Universe, the gerudo are all females, they kidnap, violate and bring back hylians to their caves.So their race keep going. They have a matriarch that is challenged into violent and deadly fight for the control of the clan.And they are all warriors in nature, blood, and genes.Fuck, even some sick bastards think about Urbosa legs.
And when a male appear, he becomes the king of the Gerudo.
In this universe we have a ratio of 70/ 30% between males and females, they dont rule on matriarch, but the females are stronger than most elite orcs.That means females can protect the babies from a rampage, and castrate some of them in a furious rage if they cannot handle their mushroom wine.So it is not like their chances of survival are innexistent,.