Doesn't sugar (3-5%) or Castor Oil (5-8%) help the same way? Or does aloe vera give something more to the properties of the soap bar apart from marketing purposes?
Castor helps to stabilize the lather, sugar adds to lather but I think it also affects the strength of the bubble wall, improving it. I don't know if aloe's effect is from natural sugars but it really does seem to make the lather fluffy and light and increase it somewhat. If you are a big fan of dense creamy lather, aloe may not be for you.