Firstly how do you know they receive tax credits? Even if they are, it doesn't mean that they are scroungers. New laws mean that in a two parent family if only one parent works they must work a minimum of 30 hours per week to qualify ie almost full time. Many jobs offered now are 28 hours per week therefore under the threshold, resulting on many people on means tested benefits when they really don't want to be (but that is a side issue)
Different families can live on different amounts. We are very frugal, buy nearly all clothes etc from carboot sales/charity shops. I put my child benefit into trust fund for my childrens university fund. Most fruit/veg is from supermarket bargain section. We could easily afford to go on holiday every year. I have friends though where both husband /wife are earning £30k+ EACH. They complain constantly about never having any money, but when you look at how they manage money very poorly it isn't surprising they are in debt.
So YABU