As it stands at the moment, the government gives councils funding for bus passes, which includes a statutory sum for those people of retirement age and the disabled. It is then up to individual councils and devolved nations to decide who they will offer passes to.
I live in Kent, and my husband was given a pass on the date of his retirement, at 60. I am disabled, and be a use I am unable to travel independently I have a bus pass which allows myself and a carer to access free bus travel.
We are hoping to move to Cambridgeshire in the future, they offer bus passes for those of retirement age, and the disabled but, not for a carer. It just depends yet again a postcode lottery!