Because they could afford it. The Roman education system was based on the Greek system, so why not learn it in Greece. The Romans education was based on the classical Greek tradition but infused with Roman politics, cosmology, and religious beliefs. The only children to receive a formal education were the children of the rich. The very rich families employed a private tutor to teach their children. Those that could not afford to do this used either slaves or sent their children to a private school.
Slaves were sold which means money was traded and you need money to successfully thrive and so when it ended there was no more money so they had to find different ways and it took a while.
As described in NewsRepulic, During the Guided age, as defined by author Mark Twain, during the 1870's in big cities, like Boston, Chicago, New York, Cleveland, corruption was prevalent. The new immigrants, who were mainly looked upon as the least employable, the bottom of the social status, and of little value. They were someone who is new to the country, lacking in language skills, and someone who has come here to take your job. So, for them to assimilate, to survive, many immigrants were forced to join together to provide support the local political bosses. In exchange for their loyalty and votes, the new immigrants were provided, a chance for jobs, housing, help in naturalization, business licenses, assistance in the courts and a voice in the community.