Because Lucas is from the Viet Nam generation which grew up on oldschool Westerns which were either Cowboys VS Indians or factual like the one where Burt Lancaster played Massai. No wonder soldiers called Nam Indian country. If you substitute Tatooine for the Frontier then the Jawas are the semi-civilized tribes who you can get along with while the Tuskens are the renegades who'll hang you up by your legs and roast your brain over and open fire for kicks. A successful Tusken raiding party would and should look like something straight from the pages of Blood Meridian IMHO:
“A legion of horribles, hundreds in number, half naked or clad in costumes attic or biblical or wardrobed out of a fevered dream with the skins of animals and silk finery and pieces of uniform still tracked with the blood of prior owners, coats of slain dragoons, frogged and braided cavalry jackets, one in a stovepipe hat and one with an umbrella and one in white stockings and a bloodstained wedding veil and some in headgear or cranefeathers or rawhide helmets that bore the horns of bull or buffalo and one in a pigeontailed coat worn backwards and otherwise naked and one in the armor of a Spanish conquistador, the breastplate and pauldrons deeply dented with old blows of mace or sabre done in another country by men whose very bones were dust and many with their braids spliced up with the hair of other beasts until they trailed upon the ground and their horses’ ears and tails worked with bits of brightly colored cloth and one whose horse’s whole head was painted crimson red and all the horsemen’s faces gaudy and grotesque with daubings like a company of mounted clowns, death hilarious, all howling in a barbarous tongue and riding down upon them like a horde from a hell more horrible yet than the brimstone land of Christian reckoning, screeching and yammering and clothed in smoke like those vaporous beings in regions beyond right knowing where the eye wanders and the lip jerks and drools.”
This is description of a Comanche raiding party the main character's troop encountered. The way the Comanche waged war would honestly make the average SS-soldier go pale: gang rapes, slave raids, torture, senseless slaughter and savagery. These warriors raided deep into the heart of Mexico and almost stopped Manifest Destiny. The Apache renegades hiding in the Northern Sierra Madre kept slaughtering Mexicans into the 1930s. They were exterminated by vigilantes led by one tough hombre named Francisco Fimbres who wanted to avenge his wife.
