“Paramita” simply means one needs to set up the background required to attain a certain goal.
Even to achieve a mundane goal we need to set some goals and work to get there step-by-step.
So, to get to the Sotapanna stage, one needs to fulfill certain requirements. To get to the Arahant stage, those requirements/conditions are higher. Of course, to get to the Buddhahood they are much higher.