Lower prices for the consumer, ability for nations to specialize in the production of certain goods, and more efficient production are all reasons for​

Reasons for Trading.
All of the reasons explained here are aspects of a developed nation. When a nation is in the process of developing, they’re pretty much worried about establishing themselves as a nation while providing for their citizens.
Once the nation taps into its natural resources and finds a niche of production, they not only use what they produce for their own people, but can now start selling it to other nations, or trading it for other resources that are not naturally present in their environment.