Why do we have to wait ROTJ to see Aliens fighting with the rebels ???

Hi everyone.
This is my question : Why do we have to wait ROTJ to see Aliens fighting with the rebels ???
I mean this is strange don't you think ? ... There are only humans in the Alliance or what ????? Is it the consequences of a lack of budget for the ANH and ESB (and it would be easier to show only humans) or did Lucas make it because he felt that showing only humans would give a "past" to the rebellion ... you know something like : "there are only humans so the Alliance must have been created by humans"

 

The "in-universe" reason is that aliens were opprossed by the Empire and didn't have much freedom anyway, but add to that the fact that the Rebellion is hard to find (duh, I mean look how long it took the Empire), I'm sure it took a while for them start coming. The Rebellion was only officially formed a couple years before ANH.

 

Also the Rebellion's primary source of soldiers was from humans. The Rebellion was formed by humans (for the most part) and most of the soldiers in the Rebellion were composed of humans. So it is understandable why we see more humans than aliens. For the Endor battle the Rebels brought in just about everything they had, if it could fly it was used.

EU of course.

 

Plus, aliens are more expensive.

 

Yep, it's a lot easier to have one standard set of equipment for humans than a bunch of different varieties for aliens. That wasn't going to stop the Rebellion, of course, but it may have slowed them down a little. After Endor, the number of aliens kept increasing.