Question

Why does netflix take so long to get new seasons?

Answer 1

Often the company that produces the series won't license seasons to Netflix until they're "back catalogue". That's why Netflix is a season behind on things like The Walking Dead and Mad Men. AMC wants people to have to come to their service to get the current season. Netflix can only license things the producers are willing to sell them.

This is a major motivation for Netflix starting to make its own exclusive series