There are about a million infected individuals right now, and climbing, and each hospitalised patient in ITU may need these procedures several times a day. An ITU team performing the procedure might consist of 2 to 4 people and the shields should be discarded every time. The number of patients is also rising rapidly, so demand is very high.
When you see doctors and nurses in full scrubs with face shields doing their shopping, then you know you need this equipment. However if you're really concerned there are other options[0].
Maybe I'm missing something, but the page literally has a section titled "Clean and reuse your face shield" and lists the chemicals that should be used to clean it.
The doctor or nurse probably won't be able to do that process everytime they use the mask. Like other reusable hospital supplies it will be collected somewhere to be cleaned in bulk. The point above is that so many will be used in a short span of time that even a 24 or 12 hour cleaning rotation will not keep up without large numbers being available.
this should only be done when you're so screwed that you don't have clean ones available. This is literally war-time thinking. It's also completely impractical to do at hospital scale, but if it's your only option...
