Radiopilot, we're talking about receiving more than mono fm, which is robust enough it works pretty well with just the power cord antenna. Try it for clean analog stereo outside of, say twenty miles, and it's "hiss city", or if there's no hiss, it's because your radio is BLENDING TO MONO. The power cord is adequate ONLY because the radio is mono.
BOTH stereo fm, AND HD require something a little better. A rotatable whip is usually sufficient for clean reception of analog stereo or HD to say 40 miles (your mileage may vary. Obviously in hilly terrain it'll be worse, in flat terrain better), say 'wabbit ears' for 60-70 miles, and an outdoor antenna and rotor can take it to perhaps 90-110 miles for either analog stereo or rabbit ears.
The idea that nobody will put up an outdoor antenna ignores one simple fact...the outdoor antenna market is BOOMING (the first time there's been growth in perhaps three decades) BECAUSE OF HDTV. Once the antenna is up, all that's required is also hooking it to your radio for superb reception. There is nothing exceptional about any of this. The requirements for clean analog fm stereo and hd are identical...something a little better than the power cord. But in city areas, where perhaps 60 percent of the population lives, even the power cord should do. The biggest limitation, and the primary reason for physically separating antenna from radio isn't that HD is somehow "defective" or "weak"...it's that HD radios are COMPUTERS, with CPUs and lots of RF floating around inside. The antenna, ANY antenna, needs to be separated from the unit by a couple of feet so that rf generated by the radio doesn't swamp the HD information. This is solvable (by manufacturers) simply by increasing internal rf shielding.
Even power cord antennas on mono clock radios NEED PROPER ALIGNMENT...they need to be run straight, no kinks or curls. EVERY radio needs proper antenna orientation. Clock radios perform quite poorly if the power cord antenna isn't run STRAIGHT. Often moving it makes a HUGE difference. HD really isn't any more fussy than that. Place the antenna, and orient it for best reception.
People aren't nearly as "antenna stupid" as you may believe. I grew up in an era, and at a location (rural NC) where ALL tv and radio reception was over the air. So did millions of people. We're used to twiddling with antennas to bring in a better signal. My 72 year old mother was listening to the radio in her hospital room the other day. It was noisy. She rotated the whip antenna until it sounded better. She is the LEAST technically knowledgable person I know, and this was a no-brainer to her. A NON ISSUE, and a waste of good time discussing it!