The goal of the guidelines is not to prevent 100% of all cases. That goal would be impossible and unreasonable. Even with perfect compliance, the guidelines are

The goal of the guidelines is not to prevent 100% of all cases. That goal would be impossible and unreasonable. Even with perfect compliance, the guidelines are not written to prevent all transmission. Again that would be impossible and impractical. You would have to refrain from opening your doors or windows. Would have to wash all food items, all packaging, and any other items from any store, or anything shipped to your home, with some disinfectant outside of your home before bringing them into your home. You would not touch anything outside your home without using gloves, ever, and your gloves would be disposed of outside of your home... etc., etc. And not only you, but every single person, including children, would have to do all these things, and more. And the few examples I wrote don't even account at all for in-home transmission. The virus is going to spread. That's not going to be prevented. There will be many individual cases. The guidelines are just for slowing it down in aggregate numbers.