Are there any reasons FOR doing lots of throwing and breakfalls?
Well, I'm personally coming to the conclusion that what I like about the strong throws and the breakfalls is that they enable shite to express power, and uke to receive power. The better the ukemi (breakfalls, rolls, attacks, movement, ability to absorb power) the more opportunity shite has to explore the power of the waza in question. I don't think powerfull throws necessarily lead to breakfalls either...sometimes they do, sometimes they don't. It often depends on the relationship between the shite and uke. But I like to be able to have my body sufficiently trained so that it will automatically make the correct decision without my monkey brain getting involved, because often that is just too slow.
Waza is a microcosm of a relationship between shite and uke...that particular waza at that point in time can focus on the power in the relationship, the control in the relationship, the connectedness between centers, lots of things, and many things at once. The better the ukemi, the more freedom to explore and express all of those things and more.