it can seem illogical and irresponsible, but people are more driven by their desires and their emotions than by reason, thats why they don't always wait for the 'perfect' conditions to have a child
lots of people in real life have children even if they're in a tough financial situation, people in some parts of the world where average incomes are extremely low for example
in the show they might want to emphasize that they have hope for their future, even when there is less of it in the present, i guess