Bleach V: Well that was a waste of time (Fullbring? What's that?)

[Psyren]

That was a stealth gigai, one that would keep them under the radar, keep the Soul Society from tracking down and butchering them like abominations. That's how they could enjoy the relatively peaceful life they had until Aizen took off his glasses. But when the chips were down, that would still allow them to drop the gigai and take up the mask. With Mr Pink's barrier voodoo, I doubt they needed to use them at home, because even Orihime's superhuman sensitivity to Ichigo's presence had trouble overcoming it. Operating outside the warehouse, however, they would still need their gigai. Since they had no intention of hiding during the battle for the four pillars, they wouldn't have needed to bring their gigai with them.

If they weren't in gigai during the fight, where were their shinigami uniforms? As we can plainly see from both TBTP and the end of the Fullbring arc in Soul Society, their shinigami bodies still have uniforms. If they were not in gigai, they would have these uniforms during the battle as well.

Rukia performed some very watered down Kido during the Substitute arc. They could have been weak because of the gigai or because of the still-recovering-from-giving-powers-to-Ichigo, though. And the fact it was an Uruhara-made Gigai (with a prize at the bottom of the box) might matter too.

Aizen explained this at the end of the rescue arc; Rukia's gigai was designed to drain all her spiritual power away (turning her into a Plus) so as to hide her soul, and within it Urahara's Hougyoku. Hers was a unique case and does not apply to the Visored because they had no Hougyokus of their own to hide.