People do alpine starts on Whitney dayhikes because Whitney is a 22+ mile round trip versus ~16 miles for HD. Yosemite is also more convenient to large population centers, and strictly by the number of people who visit both, is surely the more popular of the two (hard as that may be to believe, given Whitney's popularity), also in part, because Yosemite is a long-standing national park. The summit of HD is also 500+/- feet higher than only the TH at Whitney, thus altitude (and AMS) isn't nearly as much of a factor at Yosemite. So as strenuous as the HD hike is, my personal opinion is that, overall, a Whitney dayhike is even more so. My guess would be that, for the foregoing reasons, and probably others, you have far more noobs (who don't know what they're really getting into, and who haven't done their "homework") who visit and hike in Yosemite (and with it, HD) than you do Whitney. Given this, it seems unlikely to me that very many of those people would be willing to do an alpine start in order to summit HD.
It is frustrating to have limits put on something that has, heretofore, been unlimited. Sadly, that is a natural outgrowth of increasing popularity and just population growth. We experience it at our family's 6 islands up in Canada which have been in our extended family since 1927. For us, at some point in the future, there will not be enough space on the total room available on all 6 of those small islands together for all the family members in existence. Whitney and HD are no different, albeit on a far grander scale than our tiny islands. Everyone should have the opportunity to "do" Whitney and HD; but if "everyone" comes at once, or in this case, wants to do HD, you run into logistical problems which are not easy to overcome, and which have the potential to diminish the otherwise grand experience for those who are there.
Given the fact that this is only the second (third?) year that the HD permit system is in place, additional time is probably still needed to iron out the bugs. Even the Whitney permit system (which has been in place far longer) changes from time to time to accomodate the changing circumstances. It will likely be the same for HD.
CaT
