I think it's just a matter of consistency across the board not to have this kind of thing. So let's say you use Glare then everyone knows exactly what you are doing but if you use it and Stone IV animation comes out of nowhere, it could confuse your allies. As for actions that don't have casting times, it could be difficult again to differentiate between the animation and/or the buff, it would require looking at both to see what exactly has been used you know.

The SMN pet glamour isn't the best example as many times (before ShB) I've had players asking me to switch pets even though I had one of the right ones out all because they could not tell which one it was (Ifrit-egi or Garuda-egi disguised as Topaz Carby). This doesn't really happen now though as Titan is no longer a tank pet, but the carby colours could still cause confusion to some people regardless.