Good point. I think technically, it is a rather simple matter. On the other hand it takes years to get anything certified in aviation, so my guess is wait another few years, cameras are already located for bird's eye views.
One more thing in the example you show: this would require to look at an additional screen and check the gears before retraction. Very impractical. I can't see any procedure to be developed in this direction. Could be useful to check an incorrect indication, but to look at the status before gears up, can't see it happening.
As the Wiki Article mentions, the cause was found to be underinflated tyres. I guess it cost less to inflate tyres than fitting cameras. Also retrofits on an old generation aircraft would be a costly exercise.
Flex