If you're self employed I think the idea is that you arrange health insurance and/or savings to cover periods of sickness.
On zero hours contracts, you are entitled to
statutory sick pay, which is £95/week for up to 28 weeks, or £380/month. As average rent of a room is £325, somebody renting a room would still have £55/month to pay their bills and buy food. Obviously if you rent an entire place, have a family, have debts or other unusual expenses you're totally f.cked.
Also, sick pay on zero hours depends on when you were "scheduled to work", which can easily be changed to zero by unscrupulous employers (i.e. most of them). Most of my friends don't get their schedules more than a few days in advance, sometimes not even for a complete week, so I don't see how that's enforceable - managers are just supposed to put their sick staff on the rota when they know they're not going to come in, I guess? lol, good luck with that.
Morally, I don't see much difference between being short-term sick or long-term sick. Anybody unable to work for health reasons still deserves to live in comfort and with dignity. However, in the specific case of epidemic diseases there is also a public safety element: we really, really need people to be able to afford to self-isolate. It might be worth the extra money to pay a few scroungers to doss about in their bedsit for a few weeks if it saves the lives of Conservative voters.