Looking at local guides' photo contributions has taught me that uploading dark photos is a very common mistake on Google Maps. This issue alone can prevent your photos from being selected as cover and featured images of places. And you will be having a hard time attracting lots of views. Photos full of brightness, color, and contrast attract attention a lot better than dark photos.
The following two illustrations demonstrate what too little and too much brightness looks like.
From too dark to too bright. Notice, how details like the top windows get invisible when the brightness is at the lowest level (- -).
The middle version is well-lit. Not too dark and not too light.
You can find even darker photos uploaded to Google Maps. They are often shot at night with not the best camera. Some cameras try to compensate but the results are grainy, brownish, and often out of focus.
Here is another example where you can see what happens to colors when a shot is too dark or over-exposed.
On Google Maps your photos compete for the attention of Maps users. And the competition is fierce with millions and millions of other photos. Being too dark is such an obvious mistake. Human eyes will always be drawn to bright and colorful images. And dark photos are never bright and colorful.
Dark images don't represent the places very well when details are lost and when many of the other photos are bright and colorful.
The good news is that you can take steps to prevent this issue:
In this tutorial, you can learn How to adjust the brightness, contrast, and saturation. You can find videos demonstrating how to improve the brightness and colors using Google Photos.
If you hope to attract more views on Google Maps you could delete old photos that are too dark. And (more importantly) avoid uploading dark photos in the future. You can also flag dark photos on Google Maps as 'Poor quality'.
Find Google's official statements about this issue in the Photo Rules. Scroll down and open 12: No shadowy lighting.
A related problem is shooting towards the light source. Learn more about backlight by hitting "Suggested next page" below.