You just realised this now? When I first found out about it, I think it was under the header of something like "FFXIII will have transformers for summons". Something like that, anyway. I've always seen them as Transformers, really.

I was not a fan of Eidolons at all. I don't like much about interactive summons, actually. I rarely use them. I used summons a lot more when they were done like they were in the earlier games. Although the boost thing on FFVIII was pretty cool. But yeah, summons in XII and XIII? Never used 'em unless I had to, really. I can't remember what they did in X but I don't think I used them much there, either...