Few people realize that America had the highest standard of living in the world beginning about 1750.
The opportunity for material success attracted at least as many people as the opportunity for personal freedom.
I see you've been reading Richard Hofstadter. As he noted in America at 1750 (published posthumously),
An Englishman who traveled in America in the opening years of the nineteenth century noticed "many families, particularly in Pennsylvania, of great respectability both in our society and amongst others, who had themselves come over to this country as redemptioners [partial indentees], or were children of such."
What was true of the Pennsylvania interior in the Federal period had been true across the mountains in the Delaware and Susquehanna valleys 40 years earlier.
In the 17th and 18th centuries they mostly came for religious freedom, and to get out from under landlords and squirearchs and other squeezemeisters, and acquire real property of their own.