The problrm is that you can't get the 3000 credits and the additionzl xp needed to raise 4 stats or raise 3 and buy the talents needed to be an effective character at the start. So that leaves you the choice to gimp your charcter in the long run (because everybody knows that the best way to build a character is to raise as many stats as you can) or have an effective character without any decent gear. Considering players always riase stats they always start undergeared. If you take the Gadgeteer of hour example with the 500 starting credits he can either buy the armor or the heavy blaster pistol he needs to do his job (the iconic blaster carbine is already out of budget). So he either goes adventuring armored and armed with a toothpick or goes hunting criminals dressed like Han Solo, which is absurd. The choice between superb gear (+ 3000 credits) or a competent character (+10 xp) is absurd itself. With a bit more starting money you could easily build your charcter better and more in line with any concept more complex than "Ezra Bridger before Rebels pilot airs".
Not everybody wants to play an absolute rookie, and even mildly experienced characters have both some talents and good gear for their job. Starting credits as RAW forbid that.
Tl;dr starting money is too low to get a decent starting gear for most of the characters, starting with 1000 credits would be better without being OP