This has something mostly to do with one's body clock.

It is a scientific fact that the human adult body needs at least 7-9 hours of sleep in order to function well the next day and immediately feel refreshed after waking up. If one have had a good sleep, for sure that person will have no trouble getting out of bed. 

The problem however is not the waking up but when a person goes to sleep. Often times, teenagers and young adults have inconsistent sleeping schedules. They just sleep whenever they want or  when their body feels like resting. 

This is the major reason that leads to people having trouble getting out of bed and can be easily solved by having a stable and consistent sleeping schedule, allowing one to get a good amount of sleep.