Behavioral science.
Have you ever seen those adverts for sensodyne toothpaste?
The logic goes something like this, "I've been using sensodyne toothpaste, and I haven't been having any sensitivity. Guess I don't need to use sensodyne toothpaste..."
In this context it would go something like this, "We've stopped going out, stopped social gatherings, yet there is no widespread infection taking place, guess we can all go back to normal now then..."
In a perverse kind of way, you will need the spread to increase and you will need people to see a need for the action, before you take it, otherwise people will be half arsed about it, which is the last thing you want. You do it as late as possible, for as short a time as possible, and it is most effective. If you do it as early as possible, for as long as possible, it is least effective.
Once you understand that this is the logic, you also realize that actually deciding for yourself to start restricting your movements and social interactions would actually be a good idea on an individual level, even if giving that advice on a community level would risk it's overall effectiveness.
Totally agree with the underlying psychology of this.