Couple of things from my anecdotal experience. Firstly, people already do this, yeah there are less cyclists in winter but the dedicated still ride. Secondly, nobody is advocating for bikes and nothing else, bike infrastructure in combination with a proper public transport system. Finally I see older people riding bikes regularly, often with a grandkid on the back or front and I'd guess they're in better shape for it.
Why does everything have to be discussed in absolutes? It can be the default choice for most people most of the time and yet you've decided that it can't ever be because of a small set of scenarios in which you've decided it doesn't work. Like I said, not advocating for bikes and nothing else but the default choice for most people should not be owning and driving a car everywhere, electric or not.
