I hate the culture of downvoting for simple questions that might seem obvious. If you're lurking and reading this, stop doing that.

My understanding is that no ISP makes it public that they block a large number of sites despite the fact that they are currently technically allowed to do so, but there are a number of isolated incidents of small and short-term access issues that may charitably be mistakes, and also throttling on a site-by-site basis does definitely exist and is employed by a number of ISPs. This regulation does more preventing a backslide into corporate rule and less uplifting our current conditions.