Ewoks also makes more sense from an Imperial perspective
"Sir, should we put the shield generator for the Death Star on this planet full of dangerous 8 foot tall monsters that can rip our arms out? Or this planet where the indigenous life are 4 foot tall teddy bears?"
They fit in with the framework of Yoda's teaching too, which I love:
"Size matters not. Judge me by my size, do you?"
The Force is a metaphor for for one's inner power, abilities and potential. The empire underestimated the Ewoks/dismissed them as teddy bears and payed the price.
Makes sense they'd be able to defend themselves against Imperials, even if they're overpowered and need help from allies (the rebels).
Jawas are small and cute but you don't ever see anyone criticism them..