I live in PL , I am a mother myself and I must admit that I never met "matka polka" in my life. I thought they died out just like dinosaurs...
My mother couldn’t afford not to work when I was little, because it would be very difficult for us to get along. I never had any "Lego", "G I Joe's", "Transformers" and other stuff like that, but I also never run hungry nor never had any problems with lack of clothes, etc....
My mother is a working woman but at the same time a typical "matka polka". She didn't had the opportunity to have a higher education, nor never had time to develop her own hobby. She contributed her whole life to the family. She would skip buying anything for herself just that her children could go with the class for some kind of a trip, etc...
I must confess that I'm a very lazy person when it comes to doing some house work, but when I saw that woman coming back from work and immediately starting cleaning the house, washing the dishes, etc it really made my heart bleed. These days TV is promoting more self-centered life style, where number one priority is "I" rather than "you". My "matka Polka" showed me that giving more to your family and friends can also be very satisfying.
Some say that people search partners that have very similar traits to their parents. Actually I never thought about it until recently when I found out that my girlfriend aside that she is very intelligent, independent, and beautiful woman also has the best "matka Polska" characteristics. Those two women really motivate me to be a better person, and I wouldn’t want the “matka Polka” stereotype to vanish entirely. There is a side of it worth keeping.
PS: And I agree with iwona that they still exist here, predominantly among the poorer and less educated part of our society.