You are saying 1 out of 4 American workers shouldn't have kids[1].
If everybody followed your advice, a lot of pretty influential people wouldn't have been born: Steve Jobs, J.K. Rowling, Larry Ellison (OK maybe that works in your argument's favor). Jay Z. Abraham Lincoln. Barack Obama.
I wouldn't be here, either; my dad was a short-order fry cook when I was born. He worked a second job as a night janitor at PG&E when I was young.
So yeah, you'd better think long and hard about the financial aspects of having kids, but that actually applies whether you flip burgers at Mickey D's for minimum wage or flip bits at Facebook for a $150k annual salary.
Even if the financial aspects are hard, that actually isn't the hardest part of raising kids, even for poor people. And growing up poor isn't nearly as hard on kids as is growing up with bad parents.
If you want kids, the only reason you shouldn't have them is if you aren't up to the task of raising them -- for whatever reason.
That reason could certainly be financial; I'm not sure that I myself would have chosen to have kids if I was a short-order fry cook, instead of a highly-paid tech worker who is married to another one.
But I know plenty of low-income people who are awesome parents and whose examples I strive to live up to with my own kids.