I don't know if that was the "entire point" of Twitter. I am certainly glad that there is a bit of filtering. I recall the old days where most of my feed consisted of noise, today I actually get some value out of it.
Sure. But my Twitter feed is not important enough for me to do something about that. As it is, it's somewhat entertaining (I check it perhaps once a week) whereas if it was unfiltered I never would. So I am at least one person for whom it makes business sense for Twitter to filter in order to keep me engaged.