It's kinda strange, cause the FAA had an option of dealing with the fat ultralight crowd. They could have just regulated it out of existence. But, they didn't. They found a set of compromises that seem to be working pretty well. You can go part 103, and fly low and slow without any paperwork at all.
http://www.culverprops.com/back-yard-ul.php
You can step up to SP, and carry one person go a bit faster.
Or go all the way to PPL, then comm, ATP, etc.
I don't know that the 3rd class requirement being dropped for the PPL was ever on the table to begin with. I know there was a lot of talk in the GA community, but as far as the FAA, I never heard any discussion from them. Possibly I missed it, but if the SP stepped on those plans, the FAA will see that there is either no, or limited results from removing the 3rd class requirement and maybe adopt it for PPL.