The Sentinel software was created out of necessity when the original HP-1 was designed. That was the first time that Uniden touted "the entire RR database at your fingertips", and therefore they had to create software to support the ability to easily update the entire database on a weekly basis, along with firmware updates that were also now being accomplish via loading off the microSD card.
With the previous models, programming software was certainly a nice luxury to have, but it didn't preclude you from programming the scanner by hand. That was not the case with the HP-1, in fact without purchasing the Extreme Upgrade, it wasn't even possible to make changes to the programming via the touch screen, Sentinel was required.
It would've been wholly unfair for Uniden to expect third parties to write the software to support the HP-1 and subsequent models based on that "full database on a memory card" model (HP-2, x36HP, SDS), so writing their own software was part of the package deal.
That being said, I am very grateful that
@ProScan has a Favorites Editor for the x36HP and SDS series. Sentinel is utilitarian at best, whereas with ProScan we can enjoy a fully functional experience when maintaining our favorites lists.