Plus taxes weren't too high and the Persians improved infrastructure with better roads and they had this pony express-like mail service of which Herodotus said, They are stayed neither by snow nor rain nor heat nor darkness from accomplishing their appointed course with all speed. And the Persians embraced freedom of religion, like they were Zoroastrian, which has a claim to be the world's first monotheistic religion. It was really Zoroastrianism that introduced us to the good-evil dualism we all know so well, you know, God and Satan or Perry and Voldemort. But the Persians weren't very concerned about converting people of the empire to their faith. Plus, Zoroastrianism forbids slavery, and so slavery was almost unheard of in the Persian Empire. All in all, if you had to live in the 5th century BCE, the Persian Empire was probably the best place to do it, unless, that is, you believe Herodotus and the Greeks. We all know about the Greeks.