>>34967020They all have to be cute and relate to the fully evolved forms without spoiling the line right away. When you're presented your choice of the three starters each generation, it's their intention that they are all interesting and mysterious but still defined enough that you can make a confident choice and be happy as you progress with them on your team.
Fake starters are often either too simple, not showing any potential for an underlying theme, or too complex, giving away too much of the concept of each starter.