I am posting here as both a parent and a step parent - i hope you dont mind. I guess it will get a mix of responses - and believe me as someone who has 2 families I can see both sides - but you will tell from this which one im fighting for!
I split form my ex dh almost 7 years ago (we have 2 dc's together). I have never received a penny in financial support/maintainence in all these years. He just doesnt work. He is now married again to someone with 3 dc's of her own and the have a dc together and one on the way. She has never worked either. She has asked me to send "spending money" with my dc's when they visit their dad!
I can understand that they have a large family but cant see why that should mean he doesnt contibute anything to our dc's - after all they are equal (and infact his wifes 3 dc's all have other fathers too - who should support them!).
I also have 2 families to support as my dh has 2dc's also - so we pay mainatence for these, aswell as buying clothes etc for them at our house (we treat the 4 children - mine and dh's the same).
Now my ex dh has said that he will not work ever, but that when his wife has had their latest baby - then she will get a job - because it will mean they can improve their families lifetyle without having to contribute towards our children! We are struggling too - and both myself and my dh both work!