Here's what my perspective has been: a great many homes and apartments have either older wiring, mild to severe issues with grounding on cable TV wiring, or both situations and even then some. In an ideal world, none of that would be the case, but we clearly aren't dealing with ideals - the large number of complaints relating to ground loop hum and noise generated by light dimmers makes that abundantly (almost frighteningly) clear. When components can be reasonably designed to rely on a two-prong electrical connection, the gremlins derived from that old wiring and those grounding issues are less likely to cause people grief. In those cases, I have a difficult time finding fault with the companies or their designers for electing to take that approach.