They always seemed idiotically distracting to me.
Recall one many years ago, we were driving from San Diego to San Francisco up 5, got dark and there was a light sign flashing, backed us up for 5 miles slowed down to 15 mph from 70, sign said Have a nice day.
Shortly after Jerry Brown won his first term as California governor, electronic signs appeared over freeways nagging motorists about wearing seatbelts, driving under 55 mph, etc. As soon as Brown was replaced by Republican Governor George Deukmejian, the signs vanished.