Meanwhile I’m sitting here wishing Alph was indeed an Olimar echo or semi-clone so he could actually blink while idle and have his own taunts and other animations + his own ship, and that both him and Olimar had their voices. Seriously why were they treated this way ;-;
I don't think he really had any good chance for an Echo/Clone status either. 4 was the best chance, but Pikmin & Captain, the specific character all around, lacked ideas to separate them. This is the thing that made Dark Pit plausible(since Sakurai's team had very easy ideas of what to do. The Dark Pit Staff and the Electro Arm are both super easy to use assets from Uprising. Did the Rock Pikmin have easy animations to go with from any 3DS game? I think there was a 3DS Pikmin game, but I could be wrong). You also have to think of why they would, which is going to be about the Pikmin first. Look how little they care about the Captain personalities alone. You can tell it's not a priority. So you have Rock Pikmin, who couldn't even made it in as an option for Olimar. It is a new Pikmin that also requires extra model changes. Just being a Trophy won't cut it. They need to fully animate as well. If the Rock Pikmin didn't show up in a 3DS game where they normally move, it gets harder to reuse that asset to make it fast.
For Ultimate, there's not a lot of demand for Pikmin & Alph either as a character. Coupled with no new games or re-releases, there's even less priority. The focus is blatantly intended to be on the Pikmin to a lot of the degree, and Solimar/Salph isn't exactly treated like a favorable way to play. Sakurai even lampshades how useless Olimar is(in Brawl) without the Pikmin on the character page. Once 4 comes around, you can't do a true Solimar either(thanks to the Up B now being a Pikmin, not a Pikmin Chain anymore). While it's small, he is showing that they're always a core part of the character. So making an echo isn't just about Alph, it's also about the Pikmin. So low priority plus no new Pikmin ideas and it adds up a lot why it wasn't really odd at all why they weren't remotely split off.
Don't get me wrong, I dislike how personality-less they are too. Not the lack of voices, but they could at least slightly make their taunts look more accurate to the character, without changing the animations so they affect gameplay, at the very least. Voices would be fine of course, if not encouraged.