Why was kublai khan relucant to let the polo family leave china?

Kublai Khan was reluctant to let the Polo family leave China because he valued their services and the knowledge they brought from the West. The Polos had established a strong relationship with the Khan, serving as diplomats and advisors, which he found beneficial for maintaining trade and connections with Europe. Additionally, their departure could have been seen as a loss of valuable allies in his court, especially given the political and economic complexities of the time.