Why were there many colonies in Greece and few in Rome?

The bottom line is that the Greeks rarely planned military expansion. They founded colonies with the aim of developing trade, expanding land. At the same time, the policy of Rome was based on the total expansion of the entire known world. They conquered state after state. We can say that if the Greeks built colonies, then Rome was often engaged in destruction. So, for example, in 146 BC the Romans destroyed Carthage and Corinth in order to eliminate their competitors.