I would say the main reason for the number of draws is that at the GM level, players are much more evenly matched and have a mutual respect for each other's skill. As far as playing on hoping for an opponent to blunder, I would only add that you too are risking making a blunder. There are still some GMs who try to win every game, but many engage in a policy of "not losing", and are less apt to play into double-edged or risky positions.

According to theory, your opponent must have a weakness first. Modern day defensive technique is such that it has been said that your opponent needs TWO weaknesses in order to have a winning game. Indeed, computer games have many examples of a terrible looking position that is still defendable although there is a permanent weakness in its position. But attacks may have psychological impact as well. Look at many of Shirov's and the late great Mikhail Tal's games. Sometimes attacks (warranted or not) can be helpful in the creation of weaknesses, and so we slip into a grey area, not covered by theory.

I believe in the US, it is around 1400. I do not know about other countries; England for example, has an altogether different system.