As far as I know, 75% of the trading done by institutional traders is done automatically. The traders just overview the EAs and change the algorithm parameters depending on market conditions, sentiment, economic calendar, etc. And it should be like that, when you trade large volumes you need EAs to keep you mentally healthy. Imagine opening each position with a volume of 100 lots for 8 hours/day every day.....It's just impossible not to go down emotion avenue.
Personally I trade manual because I couldn't find a good and stable EA yet and, I have to admit, I'm a bit addicted to the trading adrenaline :))))