Flight-deck video monitoring

Something I often wonder about, why do large and commercial aircraft not have the ability to view different external video views on a monitor of say crucial components ( landing gear, engines etc ) that are out of the field of view from the flight deck ? Or do they ? I’d of thought this would have been advantageous years ago.

weight/cost vs Need.
We have a lot of other systems that give the pilots tons of information. Very rare would a video inspection be needed.