Right - most people I know that have 3+ dc and are on benefits, don't WANT any more dc, but they have an issue of one sort or another with hormonal contraception (it doesn't agree with everyone - poor people don't want to get fat and moody or depressed due to contraception either), and their PCT has set arbitary age limits on sterilisation.
In my PCT, they will not put you on the waiting list for sterilisation UNTIL you are :
40 with no dc
38 with one living dc
36 with two living dc
34 with three living dc
32 with four living dc
30 with five living dc.
They will not even put you on the waiting list AT ALL if you are under 30 years old, even if you have MORE than 5 living dc.
I am 30yo, with 4 living dc. I have a disability - epilepsy - and my medication interferes with hormonal contraception, and I can't have the coil for other, medical reasons. When I am using hormonal contraception, even when taken properly, due to my meds, where other people would have a 98% chance of NOT getting pregnant while taking it properly - it is only a MAXIMUM of 85% effective in my case. Yet, due to my age, I cannot even get put ON THE WAITING LIST FOR STERILISATION in my PCT. (I have another 18 months to go before I am 'old enough' to be put on the waiting list )
And a vasectomy is all well and good - but most men in my area WON'T have a vasectomy, and the PCT won't do it unless the man has at least 2 living dc.
And also, say you have 2 dc, your DP has a vasectomy, then he leaves you. You then go into a new relationship with another man - who HASN'T had a vasectomy. If you have contraception issues - then it is an easy step to see how people end up with 3+ dc in those circumstances.