Why do we criticize single mothers

And I wonder...
Why do we criticize so much
single mothers?

Single mothers are often criticized,
we judge them very easily,
we always tend to think
that they did something wrong,
that it's their own fault,
that they are getting
what they disserve.

They are looked down upon,
they are easily judged,
and I just wonder..
why?

Why, oh why?