Why? Why is that?
Say you encountered a local situation where you meet someone in real danger, and for some contrived reason only you are able to help them (say, they knock at the door of your remote house during a blizzard or something, if it helps to make it concrete.)
The majority of society would say it is your ethical duty to help a person in such a circumstance, even at moderate inconvenience to yourself. You wouldn't necessarily be expected to sacrifice your own safety, or even your own fortune; but in general, most people would frown on your choice of a fancier car or a European vacation over someone else's life, in this kind of local, specific scenario.
So what makes that ethical obligation go away, just because it can't be pinned on any specific individual? Why does this ethical logic apply in a 1:1 scenario, but not in the many:many situation we find in society?
It does. And that is the basic ethical argument behind government welfare.
There may be room for discussion over how dire someone's straits must be before it's ethically mandatory to step in and help; fair enough. Maybe a "working senior" qualifies, maybe they don't.
But that doesn't change the underlying point. Your life is _not_ just your own. You live in a society, and that comes along with ethical obligations, both in direct circumstances of your life and indirect social issues.
We as a society shouldn't abandon a physically or mentally handicapped person to the streets anymore than we should walk whistling past someone lying on the road, injured by a hit-and-run.
Existence as human beings, and humans in society in particular, does impose moral obligations.