There are... just not in the US. They're actually a mixed bag so it's not necessarily a tragedy that the US doesn't use them:
Based on the operational studies, only the red time countdown device has a positive influence on safety and delay but increases the travel time and decreases the capacity. The pedestrian countdown signal, however, has little improvements for both travel directions.[1]
Based on the operational studies, only the red time countdown device has a positive influence on safety and delay but increases the travel time and decreases the capacity. The pedestrian countdown signal, however, has little improvements for both travel directions.[1]
[1] http://www.ce.siue.edu/faculty/hzhou/publication/What%20do%2...