Because we can't get everything, I guess.
I would personally love to have the Legacy Chocobo as its description states it's your bird from 1.0 and I had grinded to get my Chocobo whistle back then (I guess that means my bird died? q_q), buuut it's not happening. Isn't the Sylph one a reskin anyway? Pretty sure Goobbue isn't taller than Laurel Goobbue.