If I may offer a thought that is entirely my own (as far as I know), the positive-time bound commandments are masculine-style activities. Sitting outdoors in the crisp autumn in a small hut that he rapidly built with his hands is the kind of thing a man is more inclined to do. Most women prefer to be in the house, near the kitchen, where children have room to play. The same applies to wearing simple black boxes -- every single day the same style. Few women want to wear the same plain article every day. The same can be said of adhering to the regimentation of saying Shema at a specific time, every morning, no exceptions for morning sickness. The same goes for making an intentionally jolting sound with a dead Ram’s horn and waving around a lulav as if it were a sword. The positive time-bound commandments from which women are not exempt don’t have this quality. Examples include kiddush, which is said at the dinner table over wine, and eating matzah, again at the dinner table. This may not be a profound philosophical idea, but it seems to fit somewhat. Even if the generalizations are offensive to some (but mostly not to people in the Orthodox Jewish world), you have to admit, there’s truth to it.
