Think about it .. Getting abandoned 1i's through moult to 2i is really only successful when the 1i's are kept in reasonably sterile conditions.
Being on the mothers back, they benefit from the mothers natural defences. For example, we secret sweat that helps keep the skins Ph low which in turn offers us a certain amount of protection against micro organisms....most other animals, inverts included have also developed similar safeguards in one form or another.
Your normal run of the mill enclosure will be home to countless species of micro organism's with extra warmth and humidity only increasing the variety and amounts.
Therefore i would imagine any 1i's not offered the protection of their mothers immune system would quickly succumb if just left to themselves on the substrate floor.....even a reasonably clean (to the eye) one.