In the past, many women left the workplace when they married or had children and only returned (if at all) if they could fit their work round their caring responsibilities. They cared for children and then elderly or sick family members. There was also an army of middle aged women looking out for elderly neighbours or, if they were churchgoers, elderly parishioners. These women are now at work and / or looking after grandchildren. People are, I think, not as neighbourly as they used to be as community bounds have weakened. Many churches have declined and consist largely of elderly people, with fewer younger people to support them. Of course, there is a vast difference between keeping a friendly eye on a frail person, running errands and doing bits of shopping for him/her and actually providing care; very few friends and neighbours will provide that, and that is very much seen as the responsibility of whatever family the person has. In the past, frail people without family support were moved to care homes earlier. These days, they are supported to stay at home for much longer even if, in my opinion, the situation is not always very satisfactory with a meagre care package leaving the person on his/her own for most of the day.
Whilst many families do not provide hands-on care most will act as an advocate for their relative. I think that it's a pretty bleak situation if a person - particularly a person with dementia - has no family at all willing and able to step up and act as an advocate and attorney.