Why do baby kangaroos spend so much time in there mums pouch?

Young kangaroos (joeys) must stay in the pouch because this is where they receive all their nutrition. Baby Joeys are born about 2cm long, and extremely undeveloped. The baby kangaroo, or joey, emerges from the birth canal, much as any mammal young does, but it is completely blind and hairless. Moving by instinct only, it crawls up the mother's fur to the pouch, where it attaches to a teat. The teat then swells in the joey's mouth, securing it through all the mother's movement so it cannot be dislodged, until it has grown for several weeks.

Joeys spend about 6-8 months in the mother's pouch being nursed. In the initial stages, the joey stays attached to the teat until it is ready to begin being independent. A mother kangaroo is capable of having more than one joey of different ages in the pouch at the same time, feeding on different types of milk.

Baby kangaroos (joeys) and all marsupial young are born very undeveloped. They must stay in the pouch, attached to the mother's teat, from which they derive all of their nutrients for several months, and this is usually up to 9 months, not four. When born, a joey starts out the same size as a bean. While protected in its mother's pouch, it grows and develops until it is old enough to emerge.
In Australia were it is first born there can be sand storms. The mother keeps it in her pouch so it is safe.