Can someone tell me why..........at the age of 65 you lose you're Carers Allowance but dont stop caring???

I have paid into a system for 45 years but then had to give up working to look after my disabled wife, but was told you cannot get two benefits at the same time... it seems utterly preposterous to me when emigrants can claim allowances straight away without any contributions whatsoever. I find this an appalling state of affairs, after  giving the state my taxes and National Insurance over the years