As much as I am not a Tory (despite pearls), and their "your family will die" speech wasn't entirely reassuring, I think it might actually be pretty clever:

It was just terrifying enough to encourage those who CAN to start social distancing, people will work from home, children taken out of school, public spaces will become less crowded.

Those who CAN'T will still have to work, commute etc, but will benefit from the fact there are fewer people around to pass it on.

It is impossible to ask people on minimum wage jobs or zero hours contracts to stop working, or take their kids out of school. For a significant proportion of people school lunches are the only proper meal their children get. They need schools to be open, but we need those to CAN to self isolate of their own accord.