Except take up space and drag everything out. More crap that's thrown in to keep folks from getting the good stuff. There was no need to add them into the game except to pad out "rewards" with more crap.
I mean, this is kind of what I'm getting at - what rewards are there? The units, the materials for their gear (which requires you to get the recipes from gaining points in the raid) and their awakening materials. If you removed the Trust Moogles you'd just be complaining about the materials, I guess?
Would it really be that much better if there were only the FF14 units in the gacha and every summon was just 15 Thancreds? I don't really understand.
Also, if you're just really tight on unit/material slots then I kind of sympathize, but, er, these units' TMs are no great shakes, honestly - Thancred's is arguably the best of the bunch and that's a low bar. I'd say Minfilia comes second and Y'shtola's is actually the worst - healers aren't hurting for SPR and I'd generally rather have HP than DEF.