The shipping duration is actually influenced by the methods you use.
But in regards to dropship, most of the company will choose to use an economic courier option which takes a long time to arrive at the destination.
In most situations, if u use a courier of fast delivery will cost more than the product value. That's the reason why shipping one is slow.
Take USA for example, the fastest delivery to ur door step can be within 3 business days after the goods was collected by a Chinese shipping company.