Yes people who go out and have kids without thinking through how they will provide for them usually have to work pretty hard at first. Still most of the people I've seen in this situation aren't really as bad off as they think. If you didn't plan for having kids, you likely aren't in very good control of your budget either and a small investment of time in learning how to manage and budget your finances can take off most of the financial strain.

(That isn't to say there aren't some people who are in really bad situations due to random events, but I still find it rare to see people who are struggling from things that are/were completely outside of their control.)