why endocrine glands are called ductless gland?

The secretion they make, do not leave the glands through ducts, but pass directly into the blood circulation through the substance of the glands.

The endocrine is called the ductless glands because there is no ducts in the glands. The products such as hormones are secreted and goes directly to the blood stream. So there is no need for glands to collect and distribute the products, it just goes straight to the blood. Exocrine glands are the ones that do require ducts.

 Endocrine glands are called ductless glands because they release harmones directly into the bloodstream instead of secreting through ducts as done by glands like sweat glands, salivary glands and sabaceous (oil) glands.

They are known as ductless glands because they do not have a duct and secrete its products or secretion or hormone directly into the blood stream or the lymph system so it will be circulated to the entire body.

Ductless glands are the glands which secrete their products directly into the blood stream . Endocrine glands are ductless glands because they secrete hormones directly into the blood and which reach the target organ through blood.