Well, did they? Let us not forget that Juri's default costume in SF5 was brand new, it didn't appear in the previous game, so even if they did it in order to hide Juri's skin/body part with that, you can't really prove it since the costume didn't exist up until SF5, unlike Rachel's fiend outfit.
Free Step Dodge
ChaolanLegacy
Camel with 2 thumbs
during her pre release there was official art of juri in her new default without the black catsuit underneath, but once she got revealed in the balrog trailer she's been wearing it since. from that i just assume that she originally didn't have it and it was tossed on her in a last minute decision to cover her up
Kasumi-Phase-X
More like the common censorship practices that is used in case females are showing skin that for some reason has to be covered despite being made for a 17+ audience. Rachel's Fiend was given black suit so her bare skin isn't exposed.
SaihateDYNAMO
The difference is that Juri’s actually looks better with the catsuit underneath.