Why should I add shipping costs in my Etsy store for drop shipping?

[TrineLise]

I´m drop shipping and use Etsy for my shop.

I can´t get my head around to understand the shipping prices... The orders go through Ali express and often they don´t charge anything for shipping, or very little. Why should I add shipping in my store then? Is it some way it can get it to calculate automaticly? 

What would you recommend to do?