Because in 20 minutes when I venture out of my house, no one will seem to have a care in the world.
For what it's worth, I'm treating this a lot like Y2K. The nice thing is, I still have some of my stash left, especially non-perishables. I have picked up a couple of N95 masks in addition. I am planning on 4-6 months of spotty food and staples delivery if this thing gets really going here. Also, planning for no electricity or water, which may be a stretch. Heat probably won't be a problem at this time of year. It is possible large areas may be quarantined for a while and some business and transportation might be shut down. But, if the disease runs a full course, it could be months of disruptions.
I don't know though. Maybe I am over reacting. Anything could happen, and usually things don't get as bad as you should plan for. But, just in case...
However, if this thing gets out of the box and mortality rates run 10-15% things could get grim in our inter-dependent society, especially if staples start to run low in your area.