Accept this answer:
Chocolate and Vanilla.
There is no way that any one manufacturer will ever get it right for ALL users. Maybe they think that adding a somewhat functional harmonizer is better than none at all. Maybe if enough singers speak up (sing up?)... they will come on board and do it better, but to look for truth in a retail world is a fantasy, my friend. If it makes money ...... they will keep on selling it as is.
Treat it as what it IS:
A very good keyboard with some not-so-good added features. (Like all the rest)

eg:

Yamaha: Poor GM midi playback, and cheezy, small keys on psr line
Roland: virtually no entry in the high end market of today.
Ketron: poor allocation of polyphony
Korg: drum fills that sound like a new drummer sat in just for the fills
Technics: lackluster harmonizer
Casio: Still running to catch up to the pack. They started the whole thing, but stayed in the rear 9and the department stores)
Farfisa: good ideas, but missed the boat with function. Shoulda stuck to organs
Gem: no world wide acceptance. US Market has very little exposure to this line

Did I miss anyone's favorite brand?