It is also possible to allow manual blocking but have an automatic setting. The main problem with manual blocking is that if it isn't required, then there are probably better places to devote limited resources than an optional combat technique (that at least most traditional RPG players don't like). If it is required, then it does dramatically reduce the roll of your character's stats. When it comes down to it, though, I simply do not want to micro-manage combat, and lack the desire and coordination to use such a system in a game as long as RPGs tend to be. There are plenty of fighting games around with various combinations and chained attacks, etc (I've even played a couple that were not too demanding on timing and coordination).
