When you have a large web shop or website it is an idea to automatically generate meta description and key words. This way you don't have to manually insert these for every single page, which will take a lot of time.
Meta description and key words can be built from parent titles and general meta description and key words (company name etc.)
This will not create the best Meta descriptions and keywords but at least there will be some page related meta data.
This would be very helpful for large web shops and websites.